FAQ

 

 

For further information and advice, please read some of our frequently asked questions below.

01

Why should I be considering renewable energies in my home?

 

Climate change is now fully recognised as a global problem that needs addressing. With this there has been a series of International, European and National targets which the UK needs to meet to show it is committing to reducing carbon emissions. A breakdown of annual UK carbon emissions shows that domestic emissions are the third biggest contributor, marginally behind transport, with business emissions being the highest. This means it is vital to decrease our domestic energy usage if the UK is going to commit to the targets set.

There is a range of renewable technologies available with financial support for electricity generating systems (such as PV) and expected commitment for heat generating systems (such as solar thermal) shortly, with payments to begin in April 2011.

02

Shouldn’t we be concentrating on reducing other types of emissions, such as high polluting industry before household emissions?

 

No. Reducing emissions needs to be tackled by all end users simultaneously. Industry within the UK is now not as polluting has it has been in the past, although it does still contribute to a large amount of carbon emissions, households are significantly increasing their contribution to carbon emissions.

Domestic emissions are marginally lower than transport, but still are contributing to 27% of emissions. This means any reduction in the consumption of fossil fuels in the home will make an impact on C02 emissions. It has to be remembered to reduce C02 emission individual actions needs to take place, as well as collective.

(HM Government 2006, Climate Change the UK programme 2006 (DEFRA) cited in NHBC Foundation, 2009)

03

What are the uses of solar technologies in the home?

 

There are two types of solar use in the home. One use in the UK is for solar hot water heating (in certain circumstances a system could be used to provide a contribution to the space heating, though a larger storage volume and collector area would be required). The other use is to generate electricity through the use of photovoltaic panels.

04

What are the main advantages of Solar Water Heating?

 

Solar hot water systems have many advantages for use both domestically and commercially. Primarily, they are non-polluting as they are fuelled by the light from the Sun therefore cutting down on greenhouse emissions. Secondly, as the sun heats the water, solar water heaters save on energy reducing the consumption of non-renewables. This also, thirdly, means less energy consumptions reduce the cost of supplying hot water, reducing utility bills. Finally, by investing in solar heating water systems it shows the government and businesses that there is a demand for these technologies which can help the industry expand..

05

Will adding a solar hot water system make a significant difference to my carbon emissions?

 

Yes. A breakdown of annual CO2 emissions from a semi-detached house which will be constructed to the current Building Regulations standards Approval document shows that space heating and water heating combined account for 53% of CO2 emissions.

(NHBC Foundation, 2009- Zero Carbon homes- an introductory guide for house builders)

This shows that using passive solar design and/or active solar heating can massively reduce the emissions of your house, as well as reducing costs and increased energy security.

06

07

How do solar hot water systems work?

 

Solar hot water systems work by harnessing the solar energy released by the sun to heat hot water for use in the home. There are a variety of variations in design and products which are used, but all systems work with the same underlying principles. Water from the cold supply provides the water which is used to travel to the solar collector which, using the suns energy, heats up the water. From here it travels back into the cylinder to be stored as hot water.

Roof structure/orientation

The direction your roof is facing (orientation), the slope of the roof and shading are important factors, regardless of the type of panel you are interested in:

The position that maximises the energy collected by a solar panel in the UK is facing south and tilted at an angle of 35 degrees from the horizontal.

What many people find surprising, however is that the total energy collected in a year is not really a strong function of the direction in which the panel faces. This is especially true for panels on a roof – tilted at around 35 degrees, where the difference between facing east or west and facing due south is only around 12%. It is important to be aware that the output of the collector will be reduced on an east/west orientation so the collector area should be increased accordingly.

What is the best position for a solar collector on a flat roof?

 

At UK latitude a solar collector should always have as Southerly an orientation as possible (for optimal performance), with a 350 pitch. If the collector needs to be laid horizontally due to being in a conservation area for example, then a direct evacuated tube, oriented in an East/West position and rotated to 350 will be the most efficient.

Solar collectors can also be mounted on an a-frame on a flat roof, again at a pitch of around 350, though extra care should be taken on flat roofs to make sure that the panel is appropriately attached to the building substructure. This can mean that the panel can either require significant weighting down (approximately 1 tonne of ballast per m2) or be attached at least 600 mm into underlying brickwork to prevent wind uplift. If in doubt, a structural engineer should provide advice on this flat roof matter.

08

What is the difference between Solar Water Heating and Photovoltaic?

 

While Photovoltaic uses the sunbeams to generate electrical energy the solar thermal energy systems transform the sunbeams into warmth that can be used to provide a contribution towards hot water consumption and in some cases towards space heating.

09

Isn’t it too cold and wet in the UK for solar to work properly?

 

No, because solar collectors work even if it’s freezing cold, all they need is sunlight and we get enough of that, even on a cloudy day. An antifreeze solution circulates around the d loop of an indirect solar thermal system, protecting it from sub-zero temperatures.

The UK receives 60 % of the solar energy compared with the equator. This is equivalent to 1000 power stations. Each square metre of the UK receives between 900 – 1200 kWh of solar radiation each year.

10

Is there enough sunshine in the UK for solar energy?

 

Compared to the equator, the UK receives approximately 60% of the energy received there, ample to operate an efficient solar panel system as long as the collectors are sized according to the required output.

How much will I save on my utility bills with a solar thermal system?

 

In terms of costs you would expect to save between 30-70% on your annual heating costs (water heating makes up on average between 20-30% of the total domestic gas bill for example). If the occupant carefully follows the installer’s advice, higher solar contributions (r to 70%) will be obtained.

 

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12

How long does solar technology last?

 

Solar technology has been around for a century now, but evacuated tubes have a lifespan of around 30+ years. PV solar panels last much longer as they have no moving parts – PV panels installed in the 60`s are still working.

 

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14

Will solar panels replace my energy bills fully?

 

No, you will not be able to totally replace your current energy or power supply to the use of solar energy, but you could get with a realistic budget and the implementation of different energy sources such as a biomass and solar panel combination.

In terms of costs, with a well installed solar thermal system you would expect to save between 30-70% on your annual heating costs (if the occupant carefully follows the installer’s advice, higher solar contributions will be obtained).

A photovoltaic system will contribute to your electricity consumption with excess energy feeding back to the National Grid (for grid connected systems). Depending on the size of collector area you could contribute to a large proportion of your annual requirements – the average domestic property uses.

 

We do not use much hot water, how can this help us?

 

Current guidelines require that the water in your hot water cylinder has to stay above 60 deg C (to prevent the growth of legionnaire’s bacteria), which means your current heating appliance (gas fired boiler for example) is constantly firing up to maintain this temperature. Regardless of the amount of hot water you use your boiler or immersion heater will still be firing to keep it heated up.

The use of a solar thermal system would provide the initial contribution to this as a minimum, usually able to heat to at least 600C through many months of the year. Current best practice guidelines would suggest that 1m2 of collector area (flat plate) and 0.8m2 of evacuated tube per person should provide sufficient contribution in a domestic property.

 

15

What are the differences between the Solar Collectors?

 

There are three main types of collectors which are used within the UK

Flat Plate Collectors:

These collectors are based on a thin absorber sheet, which is unusually copper, backed by a fluid tubing system all placed in an insulated casing with a glass covering. Fluid is then circulated through the tubing which absorbs heat from the collector and transports it to the heat exchanger. The insulated casing ensures minimal heat loss from the collector, which can reach efficiencies of 75- 80%. The transparent cover protects against weather damage and prevents heat from being carried away in the wind.

Flat collectors demonstrate a good price-performance ratio as well as flexible mounting options. They can be fitted on top of existing roof coverings, however, if a new builds property they can be built into the roof forming part of the cover. They are normally the standard modules supplies for surface areas between 1 and 4sq metres.

 

Evacuated Tube Collectors:

Evacuated tube collectors have two categories:

1. direct flow evacuation tubes.

2. Heat pipe evacuation tubes.

Both of these collectors are similar in appearance, but work in different ways. Both contain evacuated glass tubes which are mounted on a frame and connected by a manifold.

Heat pipe tubes can only be installed vertically, but direct flow tubes are more flexible and can be installed both horizontally and vertically.

 

Unglazed Solar Collector

As these collectors are unglazed then absorb a high amount of the suns energy, however, they are not insulated so a high portion of the heat is lost, particularly on windy days. They are primarily used for heating swimming pools, where the pool water circulates directly through them.

 

16

Which Collector has the highest levels of efficiency?

 

Absorber plate materials will absorb radiation; it is the retention of this radiation which important. This is increased dependant on the coatings applied to the metal absorber surfaces which are either Non Selective or Selective.

Non selective surfaces are good absorbers of radiation, absorbing 90-95% of all solar radiation; however, they are also good radiators releasing 90% of the theoretical maximum heat energy. Therefore as the temperature of the transfer fluid increases the efficiency of the collector decreases.

Selective surfaces are also good absorbers of radiation, absorbing 90-95% of solar radiation which falls on them; however they are much poorer radiators and emit less than 15% of the radiation falling on them, making selective surface collectors much more efficient.

Both flat plate collectors and evacuated tube collectors have selective and non selective surfaces. In terms of which collector has best efficiency, it is dependent on your domestic use. At low temperatures the efficiency for all the collectors is very similar, but as temperatures increase all the collectors show a reduction in efficiency. For lowest temperatures an unglazed non-selective surface flat plate collector can be seen as most effective, hence use in swimming pools, however for highest temperatures there is a very marginal difference between selective surface evacuated tubes and selective surfaces flat plate collectors, with the former being the most efficient.

 

17

What size collectors will I need on my house?

 

There is no optimal collector size as it depends on a number of factors:

• Estimated hot water usage.

• The percentage of solar contribution to the annual hot water load.

• Geographical location.

• Inclination of the roof.

• Type of collector.

 

For domestic solar hot water systems it has been found that installing 1 m² of flat plate collector or ¾ of a m² evacuated tubes for each person using hot water will give satisfactory results. Heat loss through the system will be larger the smaller the collector it is, therefore not usual in the UK to install collector areas of less than 2.5m². This generally results in household systems having 2.5-4m² of flat plate collectors and 2.5-3.5m² of evacuated tubes.

Beware of underestimating the size of the collector needed, as saving in costs may be outweighed by dissatisfaction due to underperformance.

 

18

Can a solar water heating system be used in place of a traditional gas or electric heating system?

 

In order to ensure proper efficiency of your water heating system, a solar energy system must be used in conjunction with a traditional gas or electric heating system, rather than as an alternative to a traditional system.

 

19

Do solar systems produce hot water in the winter?

 

Solar systems will operate and produce hot water during the winter months; all systems contain an anti-freeze protection where applicable. The output of the system (or temperatures reached) will be lower during the winter months, though a contribution will still be received, reducing the amount of work needed by the secondary heat source (gas condensing boiler for example).

 

20

Do solar systems produce hot water on a cloudy/overcast day?

 

Solar systems will be able to provide heating during cloudy or overcast days, they operate effectively in ambient light as well as direct. Higher temperatures will of course be reached in direct sunlight though ambient should also be able to reach the required temperatures – the use of traditional gas or electric heating system (secondary heat source) may be required to achieve the required temperatures on darker and shorter days. 

 

21

What happens if one of the solar tubes is broken?

 

The tubes are very strong and not easily broken, but can be replaced very easily should one break due to extreme conditions. They are inexpensive and available via Solarfit. 

 

22

What is the payback/ROI of a solar thermal system?

 

Depending on factors including geographic location of the system, insulation levels (amount of solar radiation) in that area and annual usage of the system, an average household of 4 can expect to recover the cost of a solar system within 12-16 years depending on hot water consumption and making use of the Renewable Heat Incentive payments (due to come into effect in April 2011).

 

23

What is the life of the solar collector systems?

 

Solar systems have a life expectancy of greater than 20 years and are usually supplied with a manufacturer’s warranty of 10 years.

 

24

Do solar heating systems require any maintenance?

 

Maintenance of the system is negligible; however, an annual assessment of the solar system is recommended to help to maintain efficiency levels and to help avoid potential long term problems with the system. This could be tied in with the annual service of your existing heating system for example.

The fluid circulating in the system should be topped up or even drained down and replaced every 5 years or so – the anti-freeze component of the fluid breaks down over time and will reduce the performance of the system.

 

25

Will I be given advice on how to use the system?

 

On completion of the solar water system, we will take you through the system explaining the function of the components. We will also provide you with the installation, commissioning and maintenance instructions for you to keep for future reference, as well as the manufacture information which will be used in maintenance checks.

 

26

I currently have a Combination Boiler (Combi Boiler); will I need a new boiler system which can store hot water?

 

This will be dependent on the type of combi-boiler which you have. If your boiler is certified to accept pre-heated water then the solar system can be installed in a cold line feed. However, many combi- boilers cannot accept preheated water, so it has to be advised to not install a solar water heating system with these boilers. If you are determined to have a solar water heating system with a combi-boiler, it will be necessary to install a storage cylinder.

 

27

What is the average price of a domestic solar hot water system?

 

The cost of systems varies, but the average installed cost across the UK at the moment is £4200. This is for a system made up of 4m2 collector area, a dual-coil hot water cylinder of around 200 -250 litres volume, a controller and all necessary pipe work etc.

Please note that average cost is only indicative. Costs can vary significantly depending on your HW delivery system.

 

28

What are the planning permissions requirements to install solar panels on the roof of my home?

 

Under the ‘Permitted Development Rights’ solar panels will not be subject to planning permission on the majority of houses, however there are exceptions to this rule – conservation areas or listed buildings. Our advice would be to always consult your local planning authority before the installing a solar system.

More information regarding Planning Permission can be found at www.planningportal.gov.uk

 

29

What accreditations should I be looking for when hiring an installer?

 

The Micro generation Certification Scheme (MCS) is an independent scheme that certifies products and installers against a rigorous set of standards. The MCS is hoped to enable confidence in consumers for both the products which they purchase and in those who install them. To qualify for government grants all both the product and the installer have to achieve the MCS standards.

If your installer is able to self-certify their installation they will need to hold a Competent Persons Scheme (CPS), managed by the Department of Communities and Local Government (DCLG). This allows the competent installer to self-certify that their work complies with Building Regulations without needing to call out a Building Inspector, thus reducing fees and increasing competence of installers.

 

Solarfit are fully registered MCS installers.

For more information on the MCS can be found at www.microgenerationcertification.org and for more information on the CPS can be found at http://www.communities.gov.uk/planningandbuilding/buildingregulations/competentpersonsschemes/

 

30

Is there any support to help cover the costs of installing Solar systems in my home?

 

The Low Carbon Buildings Programme will continue to provide grants for the installation of solar thermal systems until the introduction of the Renewable Heat Incentive in spring 2011. The RHI is back datable to 15th July 2009.

In order to be eligible for the payments of these financial incentives, the installer and product must be MCS registered (or ‘Solar Keymark’ or equivalent).

 

31

Are solar water heating systems viable for large commercial use?

 

Yes. Solar water heating systems can be incorporated into commercial buildings, the capacity of the boiler and the size of the collectors will need to be increased, but this is dependent on what solar system is being used for. It would be recommended to contact one of our member companies who specialise in larger systems to obtain more information

 

Information sourced from www.solar-trade.org.uk