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Photovoltaic Systems

Solar Thermal Systems

Read the FAQ - General Section with answers to many common questions

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1. How do Thermal systems produce Hot Water?

2. Can you install a Thermal System if we have a Combi boiler?

3. What sort of Savings can be made by using a Thermal System?

4. Can Thermal Systems provide Space Heating?

5. Can you save electricity With Solar Thermal Systems?

6. Why don’t you link Vacuum Tube Collectors directly to Hot Water Tank Systems?

7. What is the Guarantee on the Tubes?

8. We have heard that Vacuum Tubes can fail - Is this true?


9) How does a PV (photovoltaic) System work?

10) What is a typical usage of electricity?

11) What size of System do you usually install?

12) Guarantees

13) What Sort of savings can I make with PV?

14) Are there any other reasons I might benefit from having a Solar PV or Thermal System?

15) What are your thoughts on other types of alternative energy?

16) Are there any people I should not get a Solar System from?

17) Finally, a few comments on Climate Change and why preventing it is important?

Frequently Asked Questions - System Specific

Solar Thermal Systems

Photovoltaic Systems



1) How do Thermal systems produce Hot Water?


By converting the suns energy into heat energy, and using that heat to warm water. Thermal Systems can absorb about 80% of the radiation striking it, and of that energy over 96% is converted to Hot Water, so only 2/3 Square metres of Collector is required, to provide up to 70% of all your Hot Water needs.


There are two main types of Collecting Panels - Flat Plate and Vacuum Tubes, heating the water in the Solar Hot Water Tank directly, or indirectly.


Vacuum Tube Collectors, are the best ones for our northern climate. The Tubes are between 35mm to 60mm in diameter, 1.4m to 2m long and made from very strong Borosilicate glass. The air inside is extracted, as the vacuum acts as an insulator, so the energy collected can’t escape, aided by dark blue selective absorbing coatings which help retain 96% of the energy landing on it.


The typical Thermal System consists of a Collector Panel, which has a number of Collecting Tubes connected to a Manifold. Solar4us use Schott Glass Panels, which has 16 Tubes per Panel. We usually we use 2 Collector Panels on a property.


A water/antifreeze mixture circulates though the Thermal Panel, collecting heat, which circulates via copper pipes, through a Solar coil in a Solar Hot Water Cylinder, where it loses that heat to heat the hot water and returns to the Thermal panel to get reheated. The heating fluid circulates via a pump, controlled by a mini computer, using information supplied by sensors on the Collectors and Solar Hot Water Tank. The System is under 6 bar pressure, so an expansion vessel, pressure safety valves and air bleeders are also installed.


Solar Heat Stores can replace Solar Hot Water Tanks. These are vented Systems, holding a fixed static amount of water in them. They have 3 coils, one for the boiler, the second for the solar that heat up the water, and then mains pressure water circulates through another coil to pick up the heat. More heat is stored than in a standard Solar Hot Water Cylinder, and all taps are at mains pressure, so you don’t need Cold Water Storage Tanks. They are more expensive than Standard Systems, and only of worth installing if you use if a lot of hot water in a short time.


All types of Thermal Systems usually allow the Boiler to be turned off in March, and not be required again until September, so savings can be made in 2 year servicing intervals, rather than one.


2) Can you install a Thermal System if we have a Combi boiler?


Yes, we can. If the Boiler is fairly new, and will accept preheated water, either a Mains Pressure Cylinder or a Heat Store is required.


If the Boiler does not accept pre heated water it can be modified to take a Standard Solar Twin Coil Tank, but the taps will not be at mains pressure, nor showers, and you need to have Cold Water Tanks installed. The better alternative is to use a vented Thermal Store, so no Cold Water Tanks are required and you have mains pressure on taps and showers.


Obviously, either of the above is a more expensive installation than connection to a Standard Boiler.

3) What sort of Savings can be made by using a Thermal System?


You will save up to 70% of your Hot Water needs.


What that is in real terms depends on the type of Fuel you normally use. Oil or Calor Gas is twice as expensive as Mains Gas. The following assumes one Fuel, only, is used for Space Heating, Hot Water production and cooking.


Although we know of people with 50% savings on their bill, we would normally expect around 30/40%. Less if one person lives in a big house, more if a lot of people live in a small terraced house. The more insulated the house, the greater the % saved. Mains Gas usually has a dual tariff at around 3.5p for the first 1500 KWh per quarter, and 2p thereafter. In the later part of spring, summer and early autumn, most of the first expensive units are used for Hot Water, so the savings will be a higher % of the total bill than the actual % of physical energy saving.


Most people underestimate their usage of energy for Hot Water. Even if you don’t use any Hot Water, 35 galls is being heated, usually twice a day, and you can tell why when you open your airing cupboard, because it’s hot from heat escaping from the HWT. Baths use around 20 galls, a shower maybe 12 galls, but if you have teenagers who stand there for 20 mins, even more than a bath. Water coming into the house is very cold, using a lot of energy to warm it. A family with two children may heat over 150 galls a day.


4) Can Thermal Systems provide Space Heating?


Both Yes and No – In fact properly designed and insulated homes hardly need heating at all, but even the latest properties, designed to this years Building Regs, are nowhere near as insulated as they should be and older properties hopeless, so to minimise heating requirements all methods of insulating and draught proofing should be the first consideration.


In houses built to the latest Building Regs up to 50% of your Space Heating needs can be met, if you link a Thermal System to an Under-floor Heating System, which only needs water temperatures of 35/45 degrees C, but you need many Solar Collector Panels, say 10/12 and a very large Heat Store. Using Solar Thermal with low temperature skirting radiator systems is a good option.


Most installers will say radiators cannot be powered by Solar Thermal Systems because the water temperature required, (75 degrees), cannot be generated by Solar Thermal in Winter, which is true as in Dec and Jan anything over 30 degrees is unlikely. However, some of the latest Thermal Stores can preheat water going into the boiler, which may provide heating for Spring and Autumn when the temperature of the water required for background heating is similar to that required for under-floor heating. Any Company that suggests they can just add an extra panel, link it to the radiators to provide Space Heating and charge several thousands of pounds is knowingly fraudulent.


The best way to get green Space heating is with biomass boilers (woodburners) having back boilers linked to radiators and also linked to the Solar Hot Water Cylinder via a third heating coil provide the remainder of the winter hot water.


5) Can you save electricity With Solar Thermal Systems?


You can also plumb the hot feed into your dishwasher and washing machine, even when they are cold feed only, to save a lot of electricity.


6) Why don’t you link Vacuum Tube Collectors directly to Hot Water Tank Systems?


We only install indirectly Solar Heated Hot Water Tanks as they are the only ones that you can ensure the water in the Hot Water Tank remains above 50 Degrees C, heated either by Solar power or through the boiler coil. This stops any chance of bacteria growing in the Tank.


7) What is the Guarantee on the Tubes?


The Tubes have a 5 year Guarantee, but we expect many, many decades of life, in reality. If a Tube becomes damaged it can be replaced individually. Each Tube would cost approx £45 plus fitting.


8) We have heard that Vacuum Tubes can fail - Is this true?


The Tubes Solar4us use, should never fail, as we use Schott Glass Tubes, the evacuated part of the Tube being solely glass.


Most of our competitors Tubes have a metal pipe running through the glass, so due to different expansion rates between metal and glass, the seal can be broken, hence the vacuum lost. Although the quality manufacturers, such as Thermomax (a British Co), have very clever joining methods, and made millions of tubes, without many failures (and we know of some 20 years old as good as new), some of the cheaper Chinese imports can, and do, fail.



9) How does a PV (photovoltaic) System work?


When the sun strikes the PV panels, which are typically 1.5m x 1m in size, direct current (DC) is produced, and converted into alternating current (AC), by an Inverter at 230 volts, which is sent to your fusebox, to power your home.


PV Panels consist of a number of Cells. Each Cell has two layers of Silicon, one doped with Boron, the negative layer (n), the other with Phosphorous, the positive layer (p). When joined together and light strikes them, the (p) layer attracts electrons from the (n) layer, hence electricity flows, and a watt or two of energy is produced. Cells vary in size from 100mm sq to 150mm sq.


50 to 70 Cells per Panel are imbedded in resin, topped by glass, and placed in aluminium frames. The average Panel produces about 200 watts at 30/40volts.


Various switches isolate each part of the system and an output meter supplied. Your Supplier may install a meter to measure the energy you export to the Grid in summer.


The best Solar PV System available is close to 20% efficiency so about 6 sq metres (5/6 panels) generate approx 1 Kilowatt of power at peak power (Kwp). 1 Kwp produces approx 1000 Kilowatt hours per year Kwh/y (Units as per your bill) from the best Panels (Sanyo).


10) What is a typical usage of electricity?


A single person living in a small property can use as little as 1500 Units. A couple, in a small bungalow, typically use 3500 Units, and a 4 person family, in a detached House, rarely use less than 4000 Units, and typically use 5/7000 units. We do come across properties where 18,000 to 30,000 Units are being consumed, if there is air conditioning or electric heating. Even underfloor electric heating uses a lot of power, but high usage can be caused by 3 Kilowatt fires left on all the time, or the immersion heater on and thermostat not in place, etc. Lots of recessed Halogen lights can significantly increase usage, as can garden or security lighting. Tumble dryers use lots of energy, plasma screens TV ‘s are big users of electricity and American style fridges can use a lot.


11) What size of System do you usually install?


We install PV Systems from 8 panels (1.5 Kwp) upwards, with 3 to 4 Kwp very popular (16/20 Panels). The Govt will pay up to 50% of the costs for domestic Systems, to a max of a 5 KWp System (24/26 Panels), producing up to 5000 Kwh/y (Units).


12) Guarantees


PV panels have power guarantees for 20/25 years, and expected to last a Century.


13) What Sort of savings can I make with PV?


If you install a PV System producing all the power you normally use, you will save all the money you would ever need to spend on electricity, forever. You can of course choose to buy a smaller System, powering a % of your needs, or even install a System which produces more than you need, and sell the power to your Supplier, at an ever increasing rate of return.


14) Are there any other reasons I might benefit from having a Solar PV or Thermal System?


Yes we can think of a few more:-


Oil and Gas Depletion - Oil and Gas will get more difficult to extract and more than half of all the Oil and Gas reserves may have gone already, and with ever increasing demand for energy, there may only be a 2/3 decades of steady supply left.


After all, we have used up nearly all the North Sea Gas and most of the Oil, and are now net importers of Gas. There is a couple of centuries of Coal left, but that is costly to make into a clean CO2 free fuel.


Buying a Solar System will help make those reserves last longer, and to some extent make you independent of that energy source. If you also use biomass boilers in the winter, you may become totally independent!


Continuity of Supply - Unless new Nuclear Power stations are brought on stream quickly, and then we use nothing but electricity, we are dependent on foreign Gas and we have seen what Russia is capable of. In fact there is limited Uranium for Nuclear Power as well.


As 40% of our Mains Electricity is generated by Gas to have independent Hot Water and a supply of electricity, independent of the Grid, even if limited for a couple of winter months, it has to be good. Many people have electricity cut off for periods, and PV is a boon for them. The comments re biomass boilers apply, as above.


15) What are your thoughts on other types of alternative energy?


Biomass Boilers

We love wood-burning stoves or wood-fired boilers, because you can use the Solar Thermal in the summer for Hot water, then switch to the wood-burner or boilers in winter, which can provide all your Heating as well. The wood-burner can have a back-boiler added to it, and you can buy log or pellet wood-fired boilers. You also need to have a third coil in the Hot Water Tank. This makes your total Heating and Hot water Carbon neutral.


Wind Turbines

Small House mounted : Most of these are a waste of time, as in urban areas there is not a consistent flow of wind, and it takes a significant wind speed to get them to produce much power. The really cheap ones may well be worn out before they save the money they cost. There is a danger to houses from the pressure against a chimney, and can shake a house in windy weather which could result in the chimney coming down on older houses.


Free Standing Turbines

If positioned where sufficient wind flow and speed they compliment PV very well, as when there is sun, there usually is no wind, and conversely, in winter, when there is less sun there is often wind.


Freestanding Turbines are more expensive than PV, for similar power outputs unless in a very windy position, but if you are in a Community, where 5/6 households can share the costs of a really big Turbine, then it is a good idea, as long as you have consistent wind. Similarly, for Schools or Commercial Buildings, large Turbines can provide a significant amount of energy. They should last for 30 years or so. We can arrange for the installation of good British made freestanding Turbines. Planning Permission is required.


NB - Vertical Rotating Turbine System

We are expecting to become the UK Agent for a Japanese Vertical Axis Turbine, soon. They work much better in urban situations, at lower wind speeds, and should last much longer. Watch this space!


Ground Source Heat Pumps

You can extract heat from the ground using a heat pump, which works well, except they use Electricity to power them. This is twice the cost of Gas so only a good idea if you only have Oil or Calor Gas, so the claims need to be halved for those on mains Gas. It still uses fossil fuel to work, so it is definitely not as Carbon Saving as PV or Thermal.


The Sunday Mirror Dec 3 2006 rated them as 2/10 as a useful alternative energy source, which is a bit harsh, but they may have a point.


16) Are there any people I should not get a Solar System from?


Solar Energy has taken off in a big way, and just as happened in Double Glazing, there are Cowboy Companies who want to overcharge you.


This mostly relates to Solar Thermal, with some Companies wanting to charge you £6300/10,000 for a System. If you asked to pay over £4500 for a Standard Thermal System, it is too much. Any Company that won’t tell you the price, until the end of a presentation, and for which they offer a subsidy on the night, for you to help promote their product in your postcode area, are not the people you should deal with.


There are 4/5 well known Cowboys Companies, often appearing on Watchdog etc! They usually send mail shots offering a subsidy, or stating they are Govt supported. They may suggest that if you help them get sales, they will pay you money, and if you sell six Systems, you will get your system free. At the end of the presentation, they say a System costs between £8500 and £10000 and up to £13000 for a radiator heating assist system, with a £2000 subsidy if you sign up now.


As we have already commented, there is no Solar System that can heat radiators, just by adding a few extra Tubes. 1 sq m of extra Tubes cannot produce more than a few watts of power in Dec or Jan, when you need the heat most, and you can’t get the radiators to the temperature they need to be to work anyway, however many extra Tubes are installed.


17) Finally, a few comments on Climate Change and why preventing it is important?


We have been warned, for over thirty years, about global warming and what will happen, but it has only recently been finally being accepted by just about everybody now. Indeed, it has taken the melting of the ice caps and rise in global temperatures to convince some people it is actually happening, now! If you still have any doubts, get the Al Gore DVD, An Inconvenient Truth, which spells out what will happen. We are at a tipping point and all of us need to start to change to a more sustainable way of living.


We managed to halt the Ozone layer from going and that is stabilising now, so we can do it.


If everyone of us made small changes to our carbon footprint, and one way, of course, is to buy one of the available Solar technologies, the problem would be solved. We know we all can also help by turning off the TV at night, putting in low energy bulbs or better insulating our houses, amongst a raft of other things.


The Stern Report, published in Nov 06, gives perhaps the most dramatic case for what will happen if we do not stop this rise in CO2. The CO2 level was 280ppm in 1780, today is at 382 and if not stabilised at no more than 550, total disaster will take place.


The findings

  • Climate change could shrink global economies by 20%

  • World temp would rise by 2 degrees C by 2050 or sooner and could rise by 5

  • Up to 200 million people could become refugees through flooding or drought

  • A 2 degree rise in temp would cause extinction of 40% of species

  • Rich nations have caused global warming but the main sufferers will be the poor nations

  • Remedial action will cost 1% of global GDP but will save £1.32 trillion

  • Govts must use tax and regulation to reduce carbon emissions and double research into low carbon technology

  • The worst impacts of climate change can still be avoided – but delay would be costly


The Solution


Lead individuals and businesses to switch away from high carbon goods, energy sources and services and to invest in low carbon alternatives.