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Heat Pumps A Best Practice Guide for businesses in Northern Ireland investni.com
Heat Pumps: A Best Practice Guide
The guide is structured to be as easy to Invest Northern Ireland
use as possible, providing an introductory Sustainable Development Team
understanding in the “Essential” sections, T: 028 9069 8868
but also satisfying those who wish to E: sustainabledev@investni.com
understand the more technical detail and
develop a feasible project in the “Advanced”
sections. Where an endnote is added for
further explanation it is indicated by roman
numerals in superscript.
2
Table of Contents
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
A. Essential – The Basics
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1 What they do. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.2 Why we need them. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 How they save energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4 What is CoP? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5 How they compare to other renewables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2. What are Heat Pumps? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.1 Heat pump types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3. Heat Pump Sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4. Permissions Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5. Financials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1 Example system costs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2 Renewable Heat Incentive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.3 Calculating income and simple pay back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4 Optimising returns from heat pumps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
7. Case Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
7.1 Inishcoo House. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.2 Abbey Haven Nursing Home. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
B. Advanced - Feasibility
8. Site Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.1 Introduction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.2 Heat sink load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.3 Calculating fabric losses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.4 Establishing ventilation losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.5 Heat emitters and distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.6 Hot water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.7 Heat source resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.8 Heat pump sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3
Heat Pumps: A Best Practice Guide
9. Understanding NIE Connection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
10. System Performance Monitoring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
11. Heat Pump Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1 Introduction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.2 Modulating compressors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.3 Enhanced vapour injection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.4 Ejector enhanced vapour compression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.5 Thermally driven heat pumps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.6 Other improvements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
12. System Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
13. Selecting Contractors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
13.2 Microgeneration Certification Scheme. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
13.3 Long-term company viability. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
13.4 Examples and references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
13.5 Servicing arrangements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
13.6 Tendering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
14. Funding and Financial Assistance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
14.2 Carbon Trust interest free loans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
14.3 Venture capital funding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
14.4 Renewable Heat Incentive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
15. Financials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
15.1 Predicting income. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.2 Capital and annual costs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.3 Pay back . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.4 Carbon savings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.5 Total return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.6 Equivalent interest. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.7 Cost per kWh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
15.8 Net Present Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
15.9 Sensitivity analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
4
16. Project Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
16.2 Site safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
16.3 In-house capabilities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
16.4 Planning the project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
GLOSSARY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
BIBLIOGRAPHY AND FURTHER READING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
This publication is not intended to be exhaustive or definitive and users of the Guide should exercise their
own professional judgement when deciding whether or not to abide by it. It cannot be guaranteed that
any of the material in the book is appropriate to a particular use. Readers are advised to consult all current
Building Regulations, EN Standards or other applicable guidelines, Health and Safety codes, as well as
up-to-date information on all materials and products.
5
Table of Figures
and Drawings
6
1.0 Table of Figures and Drawings
Figure 1 Cycle at typical CoP 10
Figure 2 Scale of automation 11
Figure 3 Renewable energy comparisons 11
Figure 4 A typical electrically driven heat pump cycle 13
Figure 5 16kW single unit ASHP 13
Figure 6 GSHP; horizontal collector 14
Figure 7 GSHP; vertical collector 14
Figure 8 WSHP; closed loop river collector 15
Figure 9 Typical CoPs 15
Figure 10 Typical CoP curves for high efficiency heat pump 17
Figure 11 Permissions Require for Heat Pumps 20
Figure 12 Example system costs 22
Figure 13 Oil boiler annual cost 23
Figure 14 Heat pump annual cost 23
Figure 15 RHI payment 23
Figure 16 Inishcoo House 27
Figure 17 Rotten timbers at Inishcoo 27
Figure 18 Wool insulation 27
Figure 19 Lime render finish, heat pump at rear 28
Figure 20 Care home savings and pay back 28
Figure 21 Pay back including RHI 29
Figure 22 Typical fabric heat loss calculation 31
Figure 23 Heat Emitter Guide excerpt 32
Figure 24 Heat Emitter Guide key 32
Figure 25 Mean monthly temperatures Aldergrove 33
Figure 26 Typical relation of ground to air temperatures 34
Figure 27 Ground temperature as a function of depth 34
Figure 28 Heat pump selection procedure 35
Figure 29 NIE connection chart 37
Figure 30 Typical monitoring display 39
Figure 31 Typical TDHP system configurations 42
Figure 32 GSHP cycle 42
Figure 33 NI RHI tariff to 1st April 2014 49
7
A Essential - The Basics
1.0 Introduction
1.1 What they do . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.2 Why we need them. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 How they save energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.4 What is CoP? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.5 How they compare to other renewables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8
1. Introduction
Introduction Heat pumps are a well proven and relatively simple
Typically, heat pumps serve the same purpose as technology, offering the opportunity to future-proof
a boiler but, rather than burning a fuel to produce our thermal energy production, stabilise costs and
heat, they move heat from a low-temperature heat grow jobs-rich industry at home. Based on current
source (ambient air, for example) and “pump” it to rates of tariffs and support, and assuming future rises
a higher temperature where it can be used to provide in energy prices, those businesses that invest capital
central heating or produce domestic hot water. to generate their heat using well designed renewable
resources will gain a competitive advantage over those
This is the same process as in a fridge or an air-
that do not. The impact of future price increases will
conditioning unit. In the case of a fridge, the heat
be diluted, enabling greater cost control. Under these
energy is pumped from the interior of the fridge to
circumstances, heat pumps can be a secure, strategic
the elements at the back. Removing this heat energy
investment opportunity for Northern Ireland business.
makes the interior of the fridge cold and the elements
at the back warm. As the elements become warmer 1.1
than room temperature, the heat energy (which was What they do
originally inside the fridge) is lost into the air of the A heat pump is a device that provides heat energy
room. A heat pump heating system does exactly the from a source of heat to a destination called a ‘heat
same thing, though on a bigger scale, and takes its sink’. Heat pumps are designed to move thermal
heat from a source outside the room – such as the energy in the opposite direction to the direction of
outside air, or the ground. spontaneous heat flow (hot to cold)ii by absorbing
heat from a cold space and releasing it to a warmer
In the cases of both fridge and heat pump, some
one, and vice-versa. A heat pump uses some external
additional energy must be supplied to the system to
power to accomplish the work of transferring energy
pump the heat from the low temperature to the higher
from the heat source to the heat sink.
temperature. There are systems that use other types
of energy to achieve this – for example, gas-heated While air conditioners and freezers are familiar
absorption fridges and heat pumps. For cooling examples of heat pumps, the term ‘heat pump’ is
applications, heat pumps mimic a fridge. more general and applies to many heating, ventilation
and air-conditioning devices used for space heating
Heat pumps are not a new technology. In 1748
or space cooling.
William Cullen first demonstrated artificial refrigeration.
In 1855 Peter von Rittinger built the first heat pump Typically, systems use the air, the ground or water
and in 1940 Robert C Webber is credited with building as the heat source and transfer the heat energy at
the first ground source heat pump. Since 2005 more a higher temperature to space heating, process
than 5.45 million heat pumps have been put into water or hot water systems.
operation in Europe. In 2012 alone, over 755,000
In a well-designed heat pump application, about 75%
new heat pumps were installed; the equivalent of
of the thermal energy produced should come directly
36 MW of heat production1.
from the heat source while about 25% will be the
The growth in heat pump use over the last 15 years primary energy used in the process cycle.
continues. As demand for efficient production of
1.2
thermal energy grows across Northern Ireland,
Why we need them
heat pumps will play a central role in our thermal
Like most developed economies, Northern Ireland
energy mix.
relies on fossil fuel derived thermal energy; primarily
A heat pump can provide heating, cooling and hot from oil and gas. Global demand for energy is
water mainly using energy from air, water or the increasing dramatically as populations grow,
ground. A unit that operates with a seasonal efficiency energy-intensive technology and economic activity
of 3 can save 66.6% of final energy, provide 100% flourishes, and immature economies develop.
of a building’s heating and hot water needs and This is happening as fossil fuel reserves diminish,
cut greenhouse gas emissions for this service by albeit slowly. As a consequence, competition for
roughly 50%. finite resources is increasing.
Historically, budget has been the principal limiting
factor when considering a heat pump installation.
The advent of the Renewable Heat Incentive
(RHI) changes the financial parameters.
9
1. Introduction
In real terms, Northern Ireland’s ‘buying power’ for 1.3
energy is extremely limited and so we are exposed How they save energy
to ever higher prices. Furthermore, 80% of the stated
The economics of heat pumps are relatively simple.
fossil fuel reserves will have to remain unburnt if we
Savings and income are derived from two sources:
are to maintain a global temperature increase rate of
less than 2°C this century and negate runaway climate SAVINGS – by using the thermal energy your heat
change. As these issues converge, the role of clean pump produces, you will buy less fossil fuel and make
energy is enhanced. savings on your fuel bill. As fossil fuel prices increase,
the savings you make should also increase.
Northern Ireland’s target is to reduce carbon
emissions by 25% from 1990 levels by 2025. INCOME – under the RHI scheme (Northern Ireland
Based on current progress it appears unlikely that Renewable Heat Incentive) you are paid for every
this will be achieved. Heat pumps can contribute unit of renewable heat energy that you produce
to any future reduction strategy. from a ground source or water source heat pump.
The payment depends on the size of system you
Heat pumps offer one of the most practicable solutions
install. Until 1st April 2015, up to 20kWthiii, you will
to the greenhouse effect. It is the only known process
be paid 8.9 p/kWh; between 20 and 100kWth you
that recirculates environmental and waste heat back
will receive 4.5 p/kWh; above 100kWth the rate is
into a heat production process; offering energy efficient
1.5 p/kWh. RHI tariffs are set annually on 1st April.
and environmentally friendly heating and cooling in
applications ranging from domestic and commercial 1.4
buildings to process industries. One key approach What is CoP?
to improving the energy efficiency of many industrial Traditionally, the performance of a heat pump is
operations is to recover every possible source of waste measured using a Coefficient of Performance (CoP).
heat and turn them into useful outputs. To facilitate This describes the ratio of useful heat produced to
this approach, the heat pump becomes a critical heat the energy consumed. Most heat pumps use
system as it possesses the capacity to recover thermal electrically driven motors and, in these cases,
energy, otherwise exhausted to environment, and the CoP is measured against the electrical
channel it to places where this heat energy can be consumption. If the heat pump produces 3kWth
converted to produce useful outcomes such as and uses 1kWeiv it will have a CoP of 3/1 = 3.
producing hot water to provide heat to occupants
in buildings. A high CoP shows good performance and lower
electrical consumption.
Heat pumps are a key technology (although no single
renewable energy technology offers a ‘silver bullet’) More recently, as a result of field trialsv, it has been
because they can be applied in many situations and demonstrated that CoP alone is not the best indicator
particularly where mains gas is not available. of value for money. System efficiency, using the energy
consumption of the entire heating system in the CoP
ratio instead of the heat pump alone, gives a more
useful factor when comparing systems. Unfortunately,
system efficiency can only be fully established in
installed systems.
Figure 1: Cycle at typical CoP
101. Introduction
The CoP of any heat pump system is optimised when Heat pumps are a mature technology, although
the temperature difference between the heat source progress continues to be made. Heat pumps require
and the heat sink is as small as possible. integration with other equipment or systems on site
and careful design is required – especially for retrofit
1.5
applications. Installation may be relatively simple (for
How they compare to other renewables
air source heat pumps (ASHP)) or complex for many
The Energy Savings Trust field trials identified that ground (GSHP) and water source heat pumps (WSHP).
the key to successful projects was good design, good Once installed, heat pumps require little maintenance;
installation and good customer briefing. Unlike many normally an annual service visit will suffice. GSHPs and
heat producing systems, most heat pumps are not WSHPs are virtually silent in operation but the design
dependent on fuel deliveries, as they run on electricity. for ASHPs must take account of noise. The only
Similarly, many heat pump installations require minimal running costs over time are electrical consumption,
client intervention once they are installed and annual servicing and, occasionally, replacement of the
commissioned. In many installations client intervention working fluid.
can be removed completely when the heat pump runs
In summary, heat pumps are relatively simple
on a demand basis. Because of this, heat pumps may
machines with a long operational lifespan and little
be seen to be highly automated when compared with
planned maintenance.
other systems.
Figure 2: Scale of automation
Heat Pump Solar Thermal Biomass CHP
Technology Maturity
High High High Medium - High
(Low, Medium, High)
Technology Complexity
Medium Low Medium - High High
(Low, Medium, High)
Installation Complexity
Medium - Low Low Medium High
(Low, Medium, High)
Project Planning Complexity
Medium Low Medium High
(Low, Medium, High)
Carbon Cleanliness
Medium High Medium - Low Fuel Specific
(Low, Medium, High)
Project Scalability Modular Modular None None
Figure 3: Renewable energy comparisons
112.0 What are Heat Pumps?
2.1 Heat pump types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
122. What are Heat Pumps
A heat pump works by reducing the pressure of However, heat pumps may also source their heat from
a liquid so that it evaporates at a very low temperature. water (ponds, rivers and boreholes) or from exhaust air,
This evaporation process needs heat, which is usually amongst others.
sourced from the ground or the air. When the vapour is
The majority of heat pumps are electrically powered
compressed from a low pressure to a higher pressure,
and fall into two distinct categories; air source (ASHP)
its boiling point is raised, so that it wants to condense
and ground source (GSHP).
into a liquid again. In order to do this it needs to
release the heat it has absorbed. The heat sink is the An ASHP takes low grade heat from the ambient
place the heat is transferred to. In most common heat outside air, using a fan to blow air across a heat
pumps the compressor is electrically driven and exchanger, carries out the heat pump cycle and
a typical heat pump cycle is shown below. Thermally transfers the high grade heat to the heat sink. There
driven heat pumps are less common and covered in are commonly two types of ASHP; an ‘air to water’
a later section of this guide. heat pump and an ‘air to air’ heat pump. The former
transfers the heat to a water based heat sink such as
a central heating system, while the latter transfers the
heat to an air heat sink such as an air heating system.
Systems may be single or split units. Single units
house the entire system and can be located inside
or outside the building. Split units normally house the
evaporator outside the building and the condenser
inside; in the same way as a traditional air-
conditioning unit.
Figure 4: A typical electrically driven heat pump cycle
(image courtesy of Element Consultants)
At point (1), the liquid is cooler than the heat source,
so heat flows naturally from the heat source into the
evaporator. This causes the liquid to evaporate.
At point (2), the vapour (from the liquid) enters the
compressor. This compresses the vapour, raising its
pressure and increasing the temperature.
At point (3), the high-pressure vapour enters the
condenser where it condenses at a higher temperature
than the heat sink; thus, heat flows naturally from the
condenser to the heat sink. At point (4), the high
pressure liquid enters the expansion valve, which
reduces the pressure to its original point, and the
cycle is complete.
Figure 5: 16kW single unit ASHP
2.1 (image courtesy of Element Consultants Ltd)
Heat pump types
Air temperatures vary seasonally and moisture content
By definition, all heat sources for a heat pump must
fluctuates so an air source heat pump will always be at
be colder in temperature than the heat sink. Most
the mercy of the climate.
commonly, heat pumps draw heat from the air (outside
or inside air) or from the ground (groundwater or soil).
132. What are Heat Pumps
The colder the air temperature, the harder the heat The pipes are filled with a working fluid, often referred
pump must work to lift the temperature up to what is to as brine, which collects the low grade heat and
required for heating. Below about 7°C, ice may form brings it back to a manifold. From the manifold, the
on the evaporator as the air is cooled, restricting the heat is transferred to the heat pump cycle via a heat
airflow and impairing performance. For this reason exchanger, and the resulting high grade heat is
ASHPs always include a defrost cycle. transferred to the heat sink. These are referred to
as ‘brine to water’ or ‘brine to air’ systems. Thus
A common defrosting method is to extract heat
a horizontal ground source heat pump installation
from the heat sink (the house or hot water tank) and
requires sufficient ground to accommodate the
resupply it to the evaporator to melt the ice – in effect,
ground loops and considerable excavation and
operating the heat pump in reverse, so that the
backfilling, in addition to the heat pump.
evaporator becomes the condenser and the condenser
the evaporator. While this is happening, heat is being GSHPs that use rock or groundwater as the heat
taken from the heat sink, and will temporarily lower source collect the heat via vertical pipe loops in
the heat pump’s CoP. An air source heat pump is a borehole or series of boreholes. A vertical collector
likely to carry the lowest capital cost of all heat is not reliant on surface area, but rather depth.
pump installations. A vertical collector usually takes the form of one or
more boreholes which accommodate a U-shaped
A GSHP takes heat from the ground. As with an ASHP,
plastic pipe configuration filled with brine for collecting
the heat can be transferred to air or water as a heat
heat. Specialist drilling equipment is required to drill to
sink. The majority of installations to date use soil as
the required depth, as well as special processes and
the heat source but rock and groundwater are also
materials (such as fusion welding and bentonite
used. The soil provides a stable temperature all year
grouting). Boreholes can be anywhere from 15 to
round with minor fluctuations at depths of 1m or more.
100m deep. For this reason, a vertical collector
The energy available in the soil is often referred to as
system can be considerably more expensive than
geothermal energy; however the vast majority of the
a horizontal collector system.
energy available in the soil at the shallow depths used
for heat pumps is solar heat (i.e. heat from the sun that WSHPs use the energy available in water and may
has been soaked up by the soil). As the temperature be ‘open’ or ‘closed loop’. A closed loop is similar to
below the ground is higher in winter than the air those discussed above where the brine constantly
temperature, GSHPs are slightly more efficient than circulates around the collector pipe work placed in the
air source heat pumps; the heat source to heat sink water source. An open loop system abstracts the water
temperature difference is smaller. Air has a lower from the water source, pumps the water past the heat
specific heat capacity than water, so to supply the exchanger, and returns it to the water source at a lower
same energy more air must be supplied to the heat temperature. Surface water, such as a river, lake or the
pump, which in turn requires more energy. Soil based sea, can be used in either a closed or open loop
systems are referred to as ‘horizontal collectors’ as system, however a closed loop system is likely to
a series of pipes must be laid below ground, typically require much less maintenance.
between 0.8 and 1.2m, to collect the heat.
Figure 6: GSHP; Figure 7: GSHP;
horizontal collector vertical collector
(Image courtesy (Image courtesy
of EHPA) of EHPA)
142. What are Heat Pumps
Protection against debris and physical damage and Another potential heat source is an exhaust air system.
obtaining the necessary permissions from the Northern These have the advantage that their heat source has
Ireland Environment Agency (NIEA) and the planning a fairly constant temperature of around 20°C, but they
authorities are also important considerations for need to be very carefully designed. They are usually
surface water collectors. Open loop systems have the installed in a passivhausvi and in commercial
ability to pollute the environment and NIEA will require applications where exhaust heat is readily available.
further risk assessments and method statements.
In addition to the electrically driven heat pumps,
In some situations an Environmental Impact
thermally driven heat pumps (TDHP) are now becoming
Assessment could be required.
mainstream. Unlike the previous heat pumps a TDHP
uses heat rather than electrical energy to power the
cycle. When comparing heat pumps driven by different
energy sources it is appropriate to use the Primary
Energy Ratio (PER); the ratio of useful heat delivered
to the primary energy input. Thus, for an electrically
driven heat pump, the CoP is multiplied by the
efficiency of the electricity generating plant to
determine the PER. In Ireland, grid electricity
efficiencies may be as low as 40%, leading to
a PER of 1.6 for a typical electrically driven GSHP.
Where waste heat, renewable heat or gas powered
heat is available, a thermally driven heat pump is likely
Figure 8; WSHP; closed loop river collector to be comparable to or outperform an electrically
(Image courtesy of Dimplex, Germany) driven heat pump.
Both absorption and adsorption can be used in the
Ground water (i.e. the water in the water table),
heat pump cycle although adsorption is less common.
because of its temperature, is an ideal heat source for
Gas absorption heat pumps (GAHP) are now
heat pumps, however, it should be noted that water
commercially available. They are perfectly suitable
must be present in sufficient quantity so that drinking
for larger buildings both for renovation and in new
water resources are not affected. This would need to
buildings, or in areas with a weak electric grid. This
be verified using test boreholes and pumping tests.
technology can achieve a primary energy efficiency
Also, when extracting from a well, the water must be
of 125–140% thus saving considerable amounts of
re-injected downstream of the groundwater flow. The
energy (up to 40% on heating costs every year
water also passes directly through the heat exchanger
compared to a condensing boiler). Lower heating
of the heat pump in an open-loop system; therefore
costs make a GAHP a cost-effective investment.
the water quality (hardness, corrosivity etc.) is an
important consideration.
For the common forms of heat pumps and well
designed, installed and maintained systems,
you may expect average CoP to be as follows:
Type CoP
ASHP 3
GSHP 4
WSHP 5
Figure 9: Typical CoPs
153.0 Heat Pump Sizing 16
3. Heat Pump Sizing
Correct heat pump sizing is essential to an efficient As a typical gas fired boiler radiator system will
and well-functioning system. Sizing is complex and work at 70–75°C, we can immediately see that the heat
should be undertaken by a suitably qualified technician delivered at 35°C will be considerably lower. The MCS
for all systemsvii. Heat pump sizing requires detailed Heat Emitter Guideviii shows that at 35°C, standard
knowledge of the heat source, the heat pump and the radiators would need to be almost seven times larger
heat sink. We have already seen that the key to to achieve the same heat output.
achieving the best CoP is to minimise the temperature
Clearly, to achieve a low flow temperature, low
difference between the heat source and the heat sink.
heat losses and the correctly sized heat emitters are
In other words, the flow temperature from the heat
necessary. The heat losses must be clearly identified,
pump should be as low as possible while still being
calculated and understood on a room by room basis.
capable of supplying the heat required at the heat sink.
If the heat losses are higher than those used for the
If the heat pump is over or under sized, or the flow
design, the heat will be lost more rapidly than the heat
temperature rises, performance will be negatively
pump can replace it at 35°C flow, and the only solution
impacted. This can be illustrated simply by examining
will be to increase the flow temperature. The heat
a typical new build space heating application.
pump will have to work harder, use more electricity and
As in any space heating application, the heat the CoP will reduce. Similarly, if the heat pump is over
losses from the building should be minimised before sized, it will cycle (switch on and off continuously) and
attempting to design a system in either a retrofit or new consume more energy.
building situation. The lower the heat losses, the less
Once the heat sink factors are established, the heat
energy will be required to heat the building and the less
pump may be addressed. The choice of heat source
power will be required from the boiler or heat pump.
will be the first consideration and this will be location
Typically, an electrically driven heat pump for a space dependent. A WSHP will require water; a horizontal
heating application will achieve its maximum CoP collector GSHP, for example, is unlikely to be possible
when delivering a flow temperature of around 35°C. unless plenty of ground is available for the collector
field; ASHPs can be installed in almost all locations.
For a heat pump designed to meet the entire space
heating load, the system will be designed to meet the
space heating requirement down to the local outside
design temperature of -3°C. Manufacturers of heat
pumps supply characteristic curves for each heat
pump on which the heating capacity in relation to
outside temperature may be plotted. These curves
are used to select the correct capacity heat pump
for the application.
Once the heat pump has been sized, the rest of the
system may be designed. For an ASHP this will simply
be the hydraulic connections and layout. For a GSHP
or WSHP the collector field must also be designed.
In each case the heat abstraction capacity of the heat
Figure 10: Typical CoP curves for high efficiency source medium must be obtained. For a horizontal
heat pump collector GSHP this will be the thermal capacity of the
(image courtesy Dimplex) soil; for a vertical collector, the thermal capacity of the
rock and for a WSHP the thermal capacity of the water.
Flow temperatures as low as this are only suitable
From the abstraction capacity of the heat source the
for low temperature heat emitters; under floor heating
collector field can be designed; the length, size and
(UFH), oversized radiators, fan assisted radiators and
spacing of collector pipe work together with the
fan coil units. At low flow temperatures, much less
necessary pumping power will be specified.
heat can be delivered to a space than at high
flow temperatures.
173. Heat Pump Sizing
In each case more specific installation detail may NIE will dictate the size of heat pump that may be
also be required. connected to the grid. When a heat pump starts it
creates high torque in the motor that in turn pulls high
In summary the following factors are paramount:
amperage. Utility companies do not like this fluctuation
• The building heat losses must be minimised on the network and limit both the size of heat pump
and carefully calculated. and the number of starts per hour that may take place.
Therefore it is important to engage with the utility
• The heat emitters must be designed for lowest
supplier at an early stage, if possible, to determine the
temperature flow possible.
maximum size available. Heat pumps are produced in
• The heat distribution system must be designed both single and three phase models. Typically, up to
prior to sizing the heat pump. 16kW with a soft start mechanism may be connected
• The heat source is established. to a single phase supply. If the size of heat pump that
you require is greater than that allowed by the utility,
• The heat pump capacity is determined using a system using a heat pump for most of the heat and
the characteristic curves. an alternative heat source for the remainder (a bivalent
• The collector field is designed. system) is common.
184.0 Permissions Required
194. Permissions Required
Permitted development rights are given to some GSHP WSHP WSHP
non-domestic microgeneration equipment (ground VC CL VC OL HC CL
and water source heat pump installations) under
Class C of Schedule 3 of the General Development Inform GSNI X X
Orderix. Certain exceptions are made including the
collector field size; distance from boundary; distance Inform/Consult NIEA X X X
from road; plant height; area occupied and protected
NIEA Abstraction Licence X
areas and buildings. ASHPs are not covered by this
permitted development.
NIEA Discharge Licence X
However, if the installation is within the curtilage of
a dwelling house, ASHPs may qualify for permitted Consult Rivers Agency X
development under Class G of Schedule 1 of the
General Development Orderx. Again there are Figure 11: Permissions Require for Heat Pumps
exceptions generally in line with those mentioned
above. Although the ASHP must be used to provide The Geological Survey of Northern Irelandxi must be
heat for use within the curtilage of the dwelling notified of any proposed borehole. The NIEA must also
house, it does not need to be used for the dwelling be consultedxii. For open loop systems an abstraction
house itself. licence will be required and a discharge consent may
Neither ASHPs nor horizontal collector GSHPs are be required. For a WSHP closed loop system in a lake
likely to require further permission. or river, Rivers Agency should be consulted.
Vertical collector (VC) systems and open loop (OL)
systems will require various other consents and
some fees may be payable. The following matrix
is not exhaustive and consultation may lead to
further requirements.
205.0 Financials
5.1 The principal legal provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.2 Underpinning regulation and best practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.3 Approved Codes of Practice for Design (Best Practice). . . . . . . . . . . . . . . . . . . . . . . 22
5.4 The duties of the designer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
215. Financials
5.1 In the context of the scheme, a non-domestic
Example system costs installation is a renewable heat unit that supplies
System costs will vary widely depending on heat pump large-scale industrial heating right down to small
type, capacity, and installation site and installation community heating projects. This includes small
details. Below we give example costs for typical businesses, hospitals, schools and so on, as well
installations using standard, good quality equipment, as district heating schemes (for example where one
Microgeneration Certification Scheme (MCS) registered boiler serves multiple homes).
installers, and installed in a standard configuration with
The RHI provides financial support for renewable heat
good access.
technologies for the lifetime of the installation (to a
The cost of designing, supplying and installing a heat maximum of 20 years). Payments will be made on
pump system as a turnkey package is subject to the a quarterly basis and determined by the actual heat
same inflationary pressure (especially on fuel, output of the system; therefore heat meters will be
insurance, labour costs etc.) as any other capital required for each installation.
project.
Under the Renewable Heat Incentive Scheme
Size (kWth) ASHP (£) GSHP (£) Regulations (Northern Ireland) 2012, the RHI tariffs
must be adjusted annually in line with the retail price
10 8,000 12,000 index (RPI) for the previous calendar year. DETI must
make the necessary calculations and publish the
20 14,000 20,000 revised tariffs and Ofgem, as administrators of the
scheme, must take account of the tariff changes and
40 20,000 28,000
ensure they are applied.
60 30,000 40,000 Under Phase 1 of the scheme (currently in place) only
GSHPs and WSHPs that transfer heat to water are
Figure 12: Example system costs supported. Gas driven heat pumps are also eligible.
(Heat Pump & Collector only: site specific) Reversible heat pumps are also eligible but only the
heat produced will receive support. ASHPs are
5.2 expected to be supported in Phase 2 of the scheme;
Renewable Heat Incentive expected to be launched in 2014.
The Renewable Heat Incentive (RHI) is a government The RHI tariffs are subject to banding; different
environmental programme that provides financial renewable technologies of differing sizes receive a
incentives to increase the uptake of renewable heat. It different tariff. Until 1st April 2015 heat pumps receive
provides subsidies to eligible, non-domestic renewable 8.9p/kWh for installations up to 20kWth, 4.5 p/kWh
heat generators and producers of biomethane based in up to 100kWth and 1.5 p/kWh for installations greater
the UK and Northern Ireland, payable for the life of the than 100kWth. All heat pumps under 45kWth must be
installation or up to a maximum of 20 years. The certified under the MCS scheme. The RHI scheme will
Northern Ireland RHI policy and tariff rates are set by be subject to review in 2014/15.
the Department of Enterprise, Trade and Investment
(DETI). Ofgem administer this scheme on behalf of
5.3
DETI. The primary objective for the RHI is to increase
Calculating income and simple pay back
the uptake of renewable heat to 10% by 2020. The
In March 2014, a typical commercial unit price for
10% target for renewable heat equates to 1.6TWh (or
electricity was 14 p/kWh, the RHI tariff was 8.7 p/kWh,
an additional 1.3TWh when considering existing levels).
for systems under 20kWth, and kerosene was 50.1 p/
This target was included in the Strategic Energy
litre or approximately 5.1 p/kWh.
Framework and an interim target of four per cent
renewable heat by 2015 has been included in the To calculate the income from a specific electrically
Programme for Government. In addition to achieving powered heat pump, system you will need to know
the set target, it is expected that the RHI will have a what size the system will be (to determine the RHI
number of other wider benefits in terms of fuel security, band), what heat it will replace and the annual cost of
lower emissions and ‘green jobs’. that heat. You will also need to know the proposed
CoP of the system and the cost of your electricity.
From these figures you can calculate the proposed
annual saving as follows.
225. Financials
Assumptions: The annual income is predicted to be £1,957.50 from the
RHI, the annual savings from the heat pump are predicted
1. You pay 14 p/kWh for your grid supplied electricity
to be £528.15.
(including VAT and levys)
Thus, from a 4kWp system, you might expect annual
2. You intend to install a system < 20kWth so the tariff
earnings of £2,485.
is 8.7 p/kWh
Simple pay back is the length of time that it will take
3. You have a 95% efficient condensing oil boiler that
for you to recover your costs. For a heat pump system
consumed 3,000 litres of oil last year at an average
the costs are the installation costs and the annual
price of 50.1 p/ litre.
maintenance costs. As we have seen above, in most
First, calculate the annual cost of running the cases, the maintenance costs are simply the cost of
oil boiler. an annual service. Thus in most cases the simple pay
back, in years, will be:
Oil Boiler Cost
Capital Cost
Annual Oil Use 3,000 litres
Simple Pay Back =
(Replaced power value +
CV Oil 10 kWh/litre
NIROC value + Export value)
Net Heat Used 30,000 kWh
Boiler Efficiency 95 % Thus, using the capital cost for a 20kWth system in
Section 5.1, Simple Pay Back will be achieved in just
Gross Heat Used 31,500 kWh over four years for this system. Note that this is a purely
hypothetical example.
Oil Cost/Litre 50.1 p/litre
Oil Price 5.01 p/kWh
5.4
Annual Cost 1,578.15 £ Optimising returns from heat pumps
Getting the best return from your heat pump system
Figure 13: Oil boiler annual cost will depend on several factors. The main
considerations are listed below:
Next calculate the annual cost of running the
heat pump. 1. Carry out a site survey to understand your
project potential.
Heat Pump Cost
2. Plan the project carefully.
CoP 4 3. Ensure the system is professionally designed
either by an MCS accredited installer or an
Heat Used 30,000 kWh
independent consultant accredited by the heat
Electricity Used 7,500 kWh pump manufacturer.
Electricity Price 14 p/kWh 4. Ensure you carry out your own calculations for
heat generation and pay back. Do not rely on
Annual El. Cost 1,050.00 £ the installer’s illustrations.
5. Ensure that the installation is correctly
Figure 14: Heat pump annual cost
commissioned and that you understand
Now calculate the RHI payment. how it operates at handover.
6. Ensure you fully understand what you will
RHI Tariff 8.7 p/kWh realistically generate and get paid.
Metered Heat 22,500 kWh 7. Ensure the system is regularly monitored and
serviced post installation.
RHI Payment 1,957.50 £
Figure 15: RHI payment
236.0 Installation 24
6. Installation
Complexity of installation will be directly relevant to For vertical collector GSHP, the process is similar
the type of heat pump installed. You will depend on except that a borehole or series of boreholes is drilled
a good, experienced contractor. to the required depth to meet the heat pump load.
High Density Polyethylene (HDPE) pipe loops are
An ASHP will be relatively simple. A single unit external
dropped down the boreholes which are then grouted
machine should be located as close to the building as
in place using a bentonite grout. This ensures heat
possible. Care should be taken to ensure that a good
transfer. If pipes are to be joined below ground level
airflow can be maintained at all times and that the
electrofusion is used to make the joint. Above ground,
unit is not in a dip, as cold air will fall and, in still
a mechanical joint may be used. Once installed and
conditions, can cause the unit to freeze up. Ideally,
connected to the manifold the same process is
heavily insulated district heating pipe should be installed
followed as above.
below ground from the heat pump foundation to the
internal space. A condensate drain must also be WHSPs will have different collector field installation
supplied at the heat pump. Once the foundation for methods depending on their design but the remainder
the heat pump has cured, the unit may be placed in of the installation will be similar to the methods
position. Internally, the buffer tank will be installed and described above.
pumps, pipe work and valves completed. Flushing is
There are many useful videos on Youtube showing
vitally important to the installation and detailed
heat pump installation, flushing and purging
guidelines for the correct procedure are laid down in
techniques. Simply search for ‘heat pump’.
the MCS guidancexiii. The controller and sensors are
connected and the system may be commissioned.
For a horizontal collector GSHP, the heat pump and
buffer tank are best installed inside the building and
the installation procedure for those elements will be
similar to that for an ASHP. The external ground work
will involve digging the collector field (normally a series
of trenches) and laying a bed of sand followed by the
collector loops (often Slinkysxiv). The Slinkys are covered
with another layer of sand to protect them before
carefully backfilling the trenches. At this point the
ground loops must be flushed and pressure tested
following MCS3005. Once complete, the ground
collectors may be connected to the external manifold
and internal flushing and purging should be completed.
Finally the system is filled with antifreeze, the antifreeze
level checked, and the system is commissioned.
253.0 Water Efficiency
7.0 Case Studies
7.1 Inishcoo House. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
7.2 Abbey Haven Nursing Home . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
267. Case Studies
7.1 Element Consultants specified lime render externally
Inishcoo House so that the walls could breathe and move; a porous
Inishcoo House is a restored eighteenth century wool insulated dry lining internally so that moisture
coastguard house standing alone on an uninhabited movement could be controlled by the hygroscopic
island off Burtonport, Co. Donegal used as a holiday action of the wool; and French drains to ensure water
let. The house comfortably accommodates 20 people. was carried away from the foundations. As an
additional protection, an electro-osmotic damp
proof course was installed.
Figure 16: Inishcoo House
The building was in an appalling state of disrepair;
mainly due to damp. Being an eighteenth century Figure 18: Wool insulation
building there is no damp proof course. At some stage
in the building’s history the external walls were cement As the only mains service is electricity, all other fuels
rendered locking in damp. In response, the owners had and materials must be transported to the island by
dry lined the interior with a waterproof membrane, boat. A heat pump system was the logical answer in
imprisoning moisture in the structure. As a result, the a building that is not permanently occupied and, being
structural timbers had rotted away. The mass rubble very close to the sea has low air temperature variation.
walls even contained peat as a building material. The layout of the building over four floors allows for
flexible letting; where only two floors may be occupied
during an overnight rental and only the ground floor for
a day rental. Therefore, the building was zoned by
floor. In order to protect the building structure, the
internal temperature must be maintained above dew
point. Rapid response by the heating system is
essential to bring the relevant zone up to comfort
temperature from dew point in as short a time as
possible to minimise energy consumption. A low
temperature under floor heating system cannot give
rapid response so domestic fan assisted radiators
were employed in each room. The on-board sensors
in these radiators control the output to the room while
a zone room thermostat shuts down the zone pump
when set temperature is reached for that zone.
Time clocks are provided for each zone. To ensure
a temperature above dew point is maintained, an
Figure 17: Rotten timbers at Inishcoo
overriding room thermostat is fitted in the coldest
north facing room. To ensure that the system cannot
The challenge was to specify a refurbishment that
freeze, an overriding frost thermostat is also fitted.
not only met building regulations and maintained
a comfortable environment but also protected the
building structure in a very hostile environment. The
only mains service on the island is 3 phase electricity.
277. Case Studies
As the building is on an unoccupied island, remote 7.2
control is essential. One of the first ‘Climote’ systems Abbey Haven Nursing Home
is fitted to allow time and temperature control by Although heat pumps are installed across the UK and
computer from anywhere in the world. Ireland in a wide variety of situations, very few have
dedicated monitoring facilities. Most people will have
A large hot water cylinder with an oversized heat
heard of high profile installations like the Giant’s
exchanger to supply the ground floor shower room,
Causeway Visitor Centre and Castle Howard but
kitchen and first floor bathroom is installed heated
few will have heard of the 180kW installation at
by the heat pump overnight at low rate night tariff.
the Riverside Hotel in Enniscorthy or the 240kW
The shower room on the second floor has an electric
installation at the ESB distribution centre in Dublin.
shower to reduce the maximum hot water demand
and the cylinder size. The Abbey Haven Nursing Home in Boyle is a 60
bedroom care home in Co. Roscommon. The home
Once the space heating load, hot water load and
is fitted with a Dimplex LA60TU heat pump and low
designs had been finalised, the heat source was
surface temperature radiators as a bivalent system
addressed. Both a water source (from the sea) and
retaining the existing oil boiler. The heat pump
an air source heat pump were considered. Although
produces approximately 80% of the energy required
more efficient, the capital costs of the civil works for
and automatically calls in the oil boiler when required
installing a water source heat pump proved too high
at low external temperatures.
and an air source heat pump was selected. Heat
loads and predicted annual energy consumption were The heating system has been closely monitored for
calculated and a 20kW system was installed. The heat over a year to determine the operating parameters
pump manufacturer was informed of the hostile salt of the system.
environment to ensure that the heat pump was
adequately protected from the environment. Heat Required 180,000 kWh
Calorific Value Oil 10 kWh/litre
Litres required 18,000 litres
Boiler Efficiency 80.00 %
Gross litres required 21,600 litres
Oil cost per litre 0.60 £/litre
Oil Cost 12,960 £
Heat from Boiler 32,000 kWh
Annual Oil Cost 2,304 £
Heat from Heat Pump 128,000 kWh
SPF 3.50
Figure 19: Lime render finish, heat pump at rear
Electricity used 36,571 kWh
The system has performed beyond expectations in its Electricity cost per kWh 0.16 £/kWh
first year, maintaining the required temperatures at the
expected cost. Annual Electricity Cost 5,851 £
Should tidal turbine technology mature, there is the Fuel Saved 4,805 £
potential to install a tidal turbine locally to provide
renewable electricity to power both the building and Installed Cost 26,500 £
the heat pump.
Pay Back 5.52 Years
Figure 20: Care home savings and pay back
287. Case Studies
If the care home were located in Northern Ireland it
would also be eligible for the RHI, leading to a pay
back in just over three years.
RHI Tarriff 2.5 p/kWh
Heat delivered 128,000 kWh
Electricity Consumed 36,571 kWh
Eligible for RHI 91,429 kWh
RHI Income 3,200 £
Total Annual Savings 8,005 £
Pay Back 3.31 Years
Figure 21: Pay back including RHI
29B Advanced - Feasibility
8.0 Site Survey
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.2 Heat sink load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.3 Calculating fabric losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.4 Establishing ventilation losses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
8.5 Heat emitters and distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.6 Hot water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.7 Heat source resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.8 Heat pump sizing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
308. Site Survey
8.1 Other software is available that calculates U values
Introduction and heat losses for the Standard Assessment
The site survey is undertaken to establish the factors Procedure (SAP)xviii. However, the SAP software uses
affecting the feasibility of an installation. Each factor a whole house calculation and various assumptions
is discussed below and each will affect the final and should not be used for calculating losses for
design, cost and ultimate feasibility. Indeed, any heat pump installationsxix.
one of the factors may stop the project in its tracks.
A typical calculation for a space is shown below with
8.2 the U value (Column 1) and area (Column 2) multiplied
Heat sink load to give the watts per centigrade (Column 3), then
In order to size a heat pump correctly, the heat sink multiplied by the temperature difference (Column 4)
must be fully understood. A typical application will to give the heat loss in watts (Column 5)
be the space heating of a building. The heat load of
a building can be calculated by adding together the
building fabric heat losses and ventilation heat losses. 1 2 3 4 5
The fabric heat losses are the sum of the losses
U Value Area m2 W/C dT (ºC) Total
through each individual part of the fabric; the floor,
the walls, the roof, the windows and the doors. Floor 0.17 104.31 17.73 24 470.10
The ventilation losses are the heat lost through
ventilating the building. Where the building has Wall 0.21 157.18 33.01 24 792.21
more than one room, the losses are a combination
Roof 0.15 143.22 21.48 24 515.59
of the losses from each room.
8.3 Windows 1.8 40.75 73.31 24 1759.35
Calculating fabric losses 445.44 145.53 Watts 3537.56
The rate of fabric heat loss is equivalent to the energy
required to maintain the desired internal temperature kW 3.54
(excluding ventilation). It is measured in watts per
square metre per degree of temperature difference Figure 22: Typical fabric heat loss calculation
between the inside and outside temperatures (W/m2C)
and is known as the U value. Thus, if we know the
area, the temperature difference and the U value for 8.4
a specific building element we can calculate the heat Establishing ventilation losses
loss for that element. Summing the heat losses gives The ventilation heat loss in a building is due
us the load required. to purpose-provided ventilation by mechanical
ventilation or natural ventilation and air infiltration or
A survey of the building will deliver the areas of air leakage. Buildings should not exceed the design
each building element by room. Each room can be ventilation rates for their purpose. It is recommended
allocated a design temperaturexv; e.g. a changing that, before installing a heat pump, the design
room might be designed to 21°C. The external design ventilation rate is established, the ventilation rate
temperature must also be set and it is better to err is measured by a specialist contractorxx, and the
on the cautious side so -3°C is reasonable although ventilation is adjusted to match the design ventilation
you may have a more accurate minimum external rate. If this policy is pursued, the design ventilation
temperature for your sitexvi. U values are provided rate may be used in the heat loss calculation.
by manufacturers of building components for most
modern building materials. However, where a building Design ventilation heat loss is established by
element is made up of more than one component, multiplying the necessary air changes per hour (ACH)xxi
the U value must be calculated. The Building by the room volume, dividing by 3, and multiplying
Research Establishment provides an approved by the design temperature difference as above.
U value calculator at a cost of £50xvii. Alternatively, Thus the design ventilation heat loss for a changing
your architect or heat pump installer will be able to room of 39m3 volume would be 10 ACH X 39 m3 =
carry out these calculations. Once each U value is 390 / 3 = 130 X 24°C = 3120 Watts.
established, the fabric heat losses may be calculated.
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