Solar Thermal Energy for Buildings in the UK: A Comprehensive Report

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SUSTAINABLE ENERGY
SOLAR THERMAL ENERGY FOR BUILDINGS IN THE UK

EXECUTIVE SUMMARY
Zero/Low carbon technologies (ZCT/LCT) are the technology that emits the low level of carbon
emission or zero carbon emission. The increasing threat of global warming and climate change has
raised the need for shifting to sustainable energy sources. The increasing demand for energy and the
cost of fuels and oil has also boosted the demand for utilizing sustainable energy sources. By
incorporating ZCTs within the buildings and other for other purposes the demand and environment
loss can be effectively eliminated. In the UK, the majority of energy use is accounted for domestic
purposes such as heating and lighting. By incorporating ZCT’s the household sector of UK can
significantly reduce the emission and achieve its vision of 80% carbon reduction by 2025. Solar
thermal energy is one of the most promising ZCT that could effectively support the UK in its vision
with sustainable development. Thus, the UK government is providing incentives for encouraging the
use of solar thermal energy and other sustainable technology among individuals and institutions.
Solar thermal technology has a great potential for fulfilling the majority of the energy demand of the
UK along with providing economic benefits to the country. Continuous research and development
will boost the potential of solar thermal technology. It can also be combined with the other ZCTs to
serve different industry needs.

Table of Contents
EXECUTIVE SUMMARY............................................................................................................. 1
INTRODUCTION........................................................................................................................3
SOLAR THERMAL AND ITS USE FOR BUILDINGS.......................................................................3
CURRENT STATE OF TECHNOLOGY USE....................................................................................4
PRESENT TECHNICAL DEVELOPMENTS.....................................................................................7
FUTURE POTENTIAL OF SOLAR THERMAL TECHNOLOGY IN THE UK........................................7
IMPACT ON THE REST OF THE ENERGY SYSTEM AND OTHER FUELS........................................8
BARRIERS AND OPPORTUNITIES TO SOLAR THERMAL TECHNOLOGY......................................9
CONCLUSION.......................................................................................................................... 11
REFERENCES........................................................................................................................... 12

INTRODUCTION
The exploitation of fossil energy sources has resulted in the increased carbon emission that has
caused a significant risk of climate change and the threat to the ecosystem. On the other hand, the
energy requirements and demand are continuously incrementing with increasing population and
changing lifestyle. Therefore, it is high time for industry revolution and transition from existing
energy sources to more affordable, accessible and sustainable energy sources. The developed
economies have already initiated planning and policy development to innovate and utilize zero-
carbon technology for reducing carbon emission as well as the developing countries have great
opportunities to encompass renewable energy and technology in its development (Xing et al., 2011).
There are many different Zero Carbon technologies (ZCT) that provide a various form of sustainable
energy such as wind turbines, tidal power, wave power, solar power, rechargeable battery, nuclear
fusion and fission, etc. These ZCT’s cut down our reliance on fossil energy sources like coal and oil
and allows local energy generation (Newbery, 2016). Out of these technologies, solar power is one
most efficient technology for the majority of the countries of the world. Solar power technology
such as solar thermal and PV panels can be effectively used to produce medium to high-density
sustainable energy (Monahan and Powell, 2011).
The UK is amongst the leading solar energy users in the world (Palmer and Cooper, 2013). This
report will thus focus on solar thermal technology for buildings or domestic use in the context of the
UK. This paper will investigate solar thermal technology by analysing the current state of technology
and its application in the UK. The report will discuss the technical developments and future potential
of solar thermal technology for buildings in the UK and how it relates and affect other parts of the
energy system and other fuel. Barriers and opportunities for using solar thermal technology in the
UK households will be assessed to understand whether or at what extent the solar thermal
technology supports in achieving the aim of zero carbon emission goal of the country.
SOLAR THERMAL AND ITS USE FOR BUILDINGS
In 2018, total energy consumption in the UK is increased by 1.1% and the domestic sector accounts
for its major part (Department for business, energy and industrial strategy, 2019). ZCT seems to be a
sustainable solution to reduce emission from buildings. Besides thermal energy storage, heat pumps
and combined heat and power, solar thermal or solar heat is recognized as the key technology for
reducing carbon emission from buildings and achieving decarbonization goals of EU (Foxon, 2013).
Solar thermal technology captures and concentrates sunlight and produces high-temperature heat
for generating electricity. Its basic principle is to utilize and convert solar energy into heat. Roof-
mounted solar panels are used in conjunction with a boiler, immersion heater or collector to
generate heat from absorbing sun rays. Active and passive are the two types of solar thermal
technology. The passive system relies on design feature to capture heat and have no mechanical
components and active system mechanical components or moving parts like pumps and fans for
circulating heat-carrying fluids (Muise, n.d).
A one-third portion of the total energy consumption in the world is constituted by the building
sector (Department for business, energy and industrial strategy, 2019). Majority of the present
world energy demand can be effective fulfilled by integrating the enormous potential of solar energy

with the local building components. The solar thermal building has emerged as an innovative
approach that supports reducing carbon emission and improving the energy performance of
buildings. Solar thermal energy is mainly used for hot water and space heating in buildings. The
technology absorbs energy from sunlight and transforms into heat that then transferred into the
heating system of a building in the form of space heating and hot water (Trenkner, et al., 2014).
Solar thermal energy is one of the best renewable energy sources for household or domestic
application. In buildings and households in the UK, solar thermal energy is increasingly used for
space heating, cooling, hot water, lightening and ventilation (Castleton et al., 2010).
[Source: Trenkner, et al., 2014]
To meet fossil energy shortage and reduce negative repercussions of climate change, it is become
critically important to use solar energy in buildings. In this regards, several organizations, architects
and contractors are responsibly practising for designing and constructing sustainable building design
to utilize solar energy to fulfil regular requirements of heating, cooling, ventilation, lighting and
space heating (Trenkner, et al., 2014).
CURRENT STATE OF TECHNOLOGY USE
European solar thermal technology platform (ESTTP) has issued a vision plan to produce 50% of the
low and medium temperature heat through solar thermal by 2030. Currently, there are over 10
million solar heat systems are installed in Europe. The UK government has a set a target to reduce
carbon emission by 80% by 2025 based on 1990 (Lees and Sexton, 2014). The UK stands at number
7th in terms of the most use of solar power (Boyle, 2019). About half of energy use in Britain
accounts for energy used for buildings and their construction. Lighting, heating, cooling, ventilation
and construction of buildings are the major sources of carbon emission in the UK. Heat and
electricity demand in homes consist of 25% of the total carbon emission of the UK. Onwards 2016,
all the new residential buildings in the UK are required to be zero carbon as a part of UK government
strategy for achieving the vision of 2025. This possesses a significant innovation challenge to the
household buildings industry to design buildings with enhancing environmental performance in the
UK. The UK government has made significant changes in the building regulations and developed the
code for sustainable homes (Lees and Sexton, 2014). The code lays down the timeline for homes to
conform to the higher levels of environmental performance with progressive changes in the building

regulations. Selection and incorporation of suitable ZCT technology are one of the major
uncertainties among builders and developers (McManus et al., 2010).
In present, solar thermal technology is mostly applied for generating hot water in small-scale plants
and urban heating networks, large-scale plants are implementing solar thermal energy for space
heating. The share of the solar thermal technology for supplying hot water to residential and non-
residential buildings is rapidly increasing. However, in Europe, solar thermal energy is also utilized
for some alternative purposes such as for district heating, solar cooling, and industrial process heat
but it represents a small percentage of total solar thermal energy use as around 90% of the new
installations are for the domestic purpose only. Currently, the use of solar thermal technology is
limited to low to the mid-rise building. 95% of the installed solar thermal technologies are used for
Hot water that too has been majorly installed by small homes. Up to 70%, annual household hot
water demand can be fulfilled by solar thermal. Space heating and hot water for household buildings
require low-temperature solar thermal energy i.e. less than 100°C (Muise, n.d).
The application of the solar thermal system is costlier as it involves several material and products.
The breakdown of the cost structure of a solar thermal system is presented below. It may vary
according to the building and design. The installation cost of accounts for 40% of total capital
investment for solar thermal (Ramos et al., 2017).
[Source: Ramos et al., 2017]
The typical investment for installing solar thermal for different family sizes for switching from gas to
solar thermal are presented below :

[Source: Mcveigh, 2017]
The support for solar water heating is continuously increasing in the UK. The government has placed
varieties of schemes to promote the application of solar thermal energy. The government is
providing direct grants, tax reductions, solar heat tariff, energy certificate and loans at reduced
rates. This directly affects the financial, economic and environmental aspects. The UK government
has also developed schemes and incentives to encourage people towards using renewable energy
for domestic purposes.
Domestic Renewable Heat Incentives (DRHI): The DRHI has been launched on 9th April 2014. Under
this scheme, the owner of the heating system receives the subsidy for using eligible renewable
energy source like solar thermal, biomass, air source and ground source heat pumps for Domestic
hot water or space heating. The owner receives quarterly payments for seven years for the amount
of clean, green and renewable heat produced by their system (Ofgem.go.uk., 2019).
Non-domestic renewable heat incentive (RHI): This scheme is useful for the non-domestic use of
eligible renewable energy sources including solar thermal. This includes small businesses, schools,
hospitals as well as district heating schemes where heating requirements of multiple buildings are
fulfilled with one installation. Under this, the owners receive payments at every quarter of a year
according to the technology and size. For solar thermal technology, the initial rate per kWh was
0.1044-pound sterling (GBP) in 2017 for 20 years (Global Solar thermal energy council, 2013).
Other than this, the Carbon trust 0% Interest loan incentive is also initiated by the UK carbon Trust.
Under this scheme, the small and medium Businesses can get interest free loans for using eligible
renewable energy like solar thermal, heat recovery and building ad pipe insulation to save excess of
carbon threshold of 1.50 tCO2 per 1,000 Pound Sterling (GBP) of loan. The loan amount ranges from
3,000 to 100,000-pound sterling (GBP). Currently, it is applicable only in wales and Northern Ireland
(Curtin et al., 2017).
The government initiatives and schemes are encouraging individual buildings, small businesses as
well as schools to install solar energy. With such initiatives, the solar energy accounts for 3.4% of the
total electricity generation in 2017 in the UK and the government also expects that by 2020 around 4
million homes in the UK will be solar-powered (Boyle, 2019). Solar thermal systems are generally
installed with the back-up heating system such as gas or oil. It could be installed in combination with
heat pumps and biomass. This also enables the homeowner to get support or incentive for both the
renewable energy systems.
For promoting the development and use of high quality solar thermal products in the UK, other
European market and beyond, solar keymark are developed. The solar keymark scheme was
developed by CEN (European Committee for Standardization) and Solar Heat Europe (former ESTIF).
It is a voluntary third-party certification mark for solar thermal products that states the compliance
of the solar thermal product with the relevant European standards. It is managed by the group of
empowered certification bodies, recognized testing laboratories, quality-conscious manufacturers
and solar heat Europe (The solar Keymark, 2019). The solar key mark scheme set standards for solar
thermal collectors and solar thermal systems, storages and controllers. The key mark is beneficial for
both consumers and manufacturers. For manufacturers, it supports a simpler testing procedure that
is valid for all European countries. It provides freedom of choice to the manufacturers with several

accredited test labs. It also simplifies the procedure introduction of new solar thermal products in
the European market and for replacing components in certified products. On the other hand, it
benefits consumers in having high quality and well-tested products and as well as also make them
eligible for subsidies (The solar Keymark, 2019).
PRESENT TECHNICAL DEVELOPMENTS
The implementation of various successful solar thermal systems worldwide results in increasing the
efficiency and cost-effectiveness of the projects with the help of continuous technological
advancements. According to research conducted by the European Solar Thermal Industry
Foundation, the power generated with the help of renewable electricity in the UK totals up to 27%
(Kathy McVeigh, 2017).
Building-integrated solar thermal (BIST) is one of the most promising technologies that are
renewable and locally available. BIST system seems like a potential solution towards reducing
emission, enhancing energy efficiency and developing cost-effective contemporary built
environment. According to Zhang et al. (2015), BIST could be defined as “multifunctional energy
facade”. The system is different from the conventional solar panels that emphasize on architectural
design features such as shape, colour and texture to utilize solar energy. It supports additional
energy production and exceptional applicability and safety in construction. BITS technology has a
great potential to boost the building energy efficiency and turn the building into an independent
energy plant. It also creates the possibilities of solar thermal energy utilization in high rise buildings.
BIST technology can be used in three types; Air-based BIST technology Water-based or Refrigerant-
based and PCM based (Zhang et al., 2015).
Solar still is also used to supply water from an area of roughly 2m2 and multiple-effect humidification
(MEH) desalination units are also utilized for indirect use of heat from highly efficient solar thermal
collectors. In addition to this, the membrane distillation technique is also used in a solar thermal
system. Active technological innovations in solar thermal technology pave a way for developments in
the industry. The new technical innovations are focusing on increasing efficiency of thermodynamic
tools to capture and convert maximum possible energy (Ramos et al., 2017). With the innovations
and development, in a new building, solar thermal technology can be installed with less cost and
well architectural design that could maximize energy efficiency and possible return on investment.
Solar technology is in a constant state of innovation, the innovations in the industry have resulted in
increased solar efficiency, increased efficiency in solar energy storage. The technical developmet5s
have brought advancements in the solar energy panel efficiency that also emphasized on lowering
the cost of product along with increased efficiency for penetration in the mainstream market. Solar
thermal fuel (STF) is developed to deal with the energy storage issues (Santamouris, 2014). The
present technical developments are bringing solar thermal technology at the forefront of ZCTs.
FUTURE POTENTIAL OF SOLAR THERMAL TECHNOLOGY IN THE UK
The scientists have told that carbon neutrality is much necessary by the end of the century to
stabilize climate change. The latest report of IPCC (Intergovernmental Panel on Climate change) has
identified many possible pathways to decarbonization that requires action in four areas viz, massive

electrification, decarbonization of electricity, improved carbon sinks and greater efficiency and less
waste in every sector.
The key advantage of solar thermal energy is that it is locally available and applicable to almost
everywhere in the UK. This system can be effectively deployed in the off-grid regions like rural areas
where power outage is a frequent problem. In addition to this, the financial incentives and support
from the government could encourage and benefit developers and owners to install a solar thermal
system (Ramos et al., 2017).
Solar thermal and passive solar technology is considered as the technology with the highest carbon
reduction potential without any unacceptable side effects. It has the potential to cover 50% of the
total heat demand. To utilize the potential of solar thermal technology, it is important to develop
new and feasible solar collectors that can be integrated with the building components. This would
also enable to open up a new and large market segment for BIST system and supports in wider
market penetration. With these developments, the BIST system can be effectively applied to the city
or district level energy supply in the upcoming years (Zhang et al., 2015).
Solar thermal technology has great potential in the European energy mix market. By 2050, it can
cover up to 47% of low-temperature needs with a proper policy framework. It represents 133
million tons of oil equivalent and enables saving of carbon emission by approximately 285,924
million tons (ESTIF, 2019). Other than reducing dependence on imports and saving energy bills, solar
thermal energy has a growing potential in industrial process heat and district heating as well as it
could also be used in other sub-sectors for cost-effective upgrading of systems with zero carbon or
pollution.
There is tremendous potential for solar thermal technology in industrial process heat as at present
there are just a few solar heat systems are available for industrial use with limited installed capacity
while the solar thermal energy has a potential to fulfil up to 40% of the industrial heating needs.
With new research and developments solar thermal technology can be effectively used for seasonal
storage, industrial applications and solar cooling up to 250°C (ESTIF, 2019). Research and
developments in the technology could also support in overcoming the issues of limited space and
sunlight.
IMPACT ON THE REST OF THE ENERGY SYSTEM AND OTHER FUELS
The energy systems are of two types, renewable and non-renewable. Non-renewable energy
systems involve the use of fossil fuel, oil, coal, natural gas and nuclear that is available in limited
supplies. While renewable energy system is those that are naturally replenished such as solar
energy, Biomass, wind energy, rain, tidal energy and geothermal heat. All these kinds of renewable
and non-renewable energy systems are being used for different purposes across the world. But, the
present environmental conditions and global warming requires a shift to sustainable energy (Zhang
et al., 2015). All the renewable sources are sustainable while all non-renewable except nuclear
energy are harmful to the environment. Here, we have discussed the solar thermal energy that is the
most promising sustainable energy sources.

Besides solar thermal technology, there are varieties of sustainable energy alternatives are available
that could support in dealing the issue of carbon emission and the use of solar energy has a direct or
indirect on the other fuels and energy system.
While comparing to Solar PV, solar thermal takes less space and works with greater efficiency. Solar
thermal do not require much space and roof areas as solar PV does. Due to this, the average
efficiency of solar PV remains between 14-20% while the average efficiency of solar thermal is 65-
75% that even with zero loss. Along with solar thermal energy, the use of Biomass and Heat pumps
are also raised significantly. But the scarcity of the biomass resources creates the necessity for
alternative energy sources. Solar thermal energy facilitates the use of
The key advantage of solar thermal energy is that it can be combined with all other kinds of backup
heat sources. As well as unlike other energy systems, it does not require electricity and can increase
power generation and transmission capacities. Several zero-carbon technologies can be effectively
used through the interplay between incremental and radical innovation. The total cost of all the
other energy and technologies depends on the unpredictable future developments whereas, the
majority of the cost of the solar thermal system is incurred at initial investment stage that facilitates
easy prediction of cost and profit.
BARRIERS AND OPPORTUNITIES TO SOLAR THERMAL TECHNOLOGY
OPPORTUNITIES
Solar thermal energy has a great opportunity shortly. In urban areas, with low space and older
housing stock in most of the cities, many buildings and properties are not suitable for any other
renewable energy source but solar thermal. Therefore, solar thermal technology is emerging as one
of the most sensible alternative energy sources for urban areas. Moreover, the average efficiency
rate of solar thermal technology is 65-75% at zero loss. In rural areas, heating is more expensive due
to the unavailability of the gas grid. So, solar thermal technology could sensible contribute to
fulfilling the demands of people residing in rural areas in a cost-effective manner. (Mcveigh, 2017]).
Solar thermal technology benefits the environment at the macro level by decreasing the dependency
over the import of fuel and avoiding carbon dioxide emissions. The technology plays a significant
role in decarbonising heating that provides various opportunities for growth to the technology and
results in the progress of the UK. The launch of Renewable Heat Incentive (RHI) in 2015 by the
government in the UK to encourage the utilization of the solar technologies among the businesses
and communities and also offering financial incentives aims to contribute 12% of heat provided by
renewable energy sources till 2020. The RHI is beneficial to the businesses in providing high returns
on investments done in solar thermal systems and can lead to higher savings by installing the
systems in the building of the companies that have a high demand for hot water. The businesses that
invest their capital in the solar thermal projects are offered with Enhanced Capital Allowance under
the Renewable Heat Incentive scheme in which the businesses can claim an allowance to the capital
on the investment done by them against the taxable profits earned by the businesses (McVeigh,
2017).
In present, there is no support for solar space heating that accounts for 20% of the total European
market. Therefore, there is an opportunity to include solar space heating in government incentives

and plans. This would result in the encouragement and development of solar thermal energy.
Therefore, if the regulations of buildings are improved in the future as predicted, the demand of
fossil fuel will decrease that would enhance the sustainability and cost-effectiveness of the solar
thermal systems (McVeigh, 2017).
Besides, individual buildings, small businesses and district heating, solar thermal systems are gaining
importance in every sector such as agriculture, mining, food, beverages, pharmaceutical and
chemical industries and the businesses in this sector are offered with great development
opportunities under the RHI scheme. Solar thermal has a bright future in the UK, not just the
individual residential buildings but also for district heating. The UK government has developed
incentives and schemes like DRHI and RHI to encourage Domestic as well as non-domestic use of
solar thermal technology.
BARRIERS
The adoption of solar thermal plants for the buildings in the UK leads to many barriers that are both
technical and non-technical.
 The installation cost of the solar thermal power is very high as it is inclusive of wiring,
batteries, inverter, and solar panels that are needed in the installation process.
 The installation and maintenance of solar thermal plants require trained and skilled
professionals like engineers, plumbers, etc. as it is a complex technology that needs
adequate skills for installation. The lack of trained professionals would act as a barrier and
lead to delay the heat uptake (Wang et al. 2015).
 The lack of space in buildings that are needed for collecting sunlight for producing electricity
can act as a hurdle for installing the solar thermal system.
 The solar energy systems cannot be installed similarly for every building, they need different
designs for different buildings depending on the client’s demand and the climate, and thus,
they are not easily adaptable and also lack flexibility (Greenmatch.co.uk., 2019.).
 The technology to be installed in the ground or the roofs of the large buildings require
special permits under the regulations prevailing in the UK which may add to the cot as the
fees and legal costs need to be paid and this legal process might lead to delays in the
installation.
 The solar thermal systems have a large dependency on sunlight for collecting solar power to
produce electricity. Therefore, the production of electricity is negligible on the cloudy or
rainy days or in winters and at night which has a noticeable effect on the solar thermal
system installed in the buildings (Wang et al. 2015).

CONCLUSION
In Summary, Solar thermal energy can be stated as a cost-competitive technology in terms of
heating and energy generation for buildings. After its purchase and installation, it provides free
energy for many years with a small investment in maintenance. Therefore it could be concluded that
the use of solar thermal technology for the building is sustainable in every aspect as it is profitable
for every stakeholder from the manufacturers, seller, users, government as well as the wider
environment. Besides, heating, cooling or lightening buildings, solar thermal energy could also be
effectively used for several other purposes like transportation, cooking, etc. the increased use of
solar power would support in curbing discharge of greenhouse gases into the air. The current state
of solar thermal energy use states that the vision 2030 would be attained successfully.
A shift to the renewable energy source is become critical due to negative impacts of the fossil energy
on climate, increasing cost, and the fact that it would not be available for all the time as it is non-
renewable. In contrast to this, renewable energy is natural and it will never run out. The
development of renewable energy sources like solar thermal will also strengthen the economic state
of the country as it will require a larger workforce and give birth to new businesses within the
country. In addition to this, solar energy is locally available that supports in eliminating the cost of
importing fossil fuels or energy from Gulf countries. One of the greatest advantages of solar energy
is reduced environmental pollution, emission and its negative impact on global climate.
In the UK, several incentives and schemes are present to encourage the use of solar thermal energy.
By encouraging and promoting the use of solar thermal energy the residents, as well as the
government of the UK, can save a significant amount of revenue as well as also strengthen the
internal economy of the country with sustainability. Therefore, from this study, it could be suggested
that the solar thermal is an best option for fulfilling the long-term heating and lightening needs of
residential and commercial buildings as well as for the industrial process. With future developments,
the majority of the heating demands of the UK are technically possible with solar energy.