• April 9, 2014 - Domestic Renewable Heat Incentive Released - Solar Thermal has got the great government funding through the Domestic RHI which it deserves! Solartwin Solar Thermal panels have just become not only a cost cutting and very green option to heat your water but now you will receive additional... More →
  • November 6, 2013 - Notice to Solartwin customers - Letter's from Stenfield & Co - A number of Solar Twin Ltd customers have been in touch this week to query a letter they have received from legal firm Stenfield & Co. - The content relates to Solar Twin Ltd's liquidation, and claims that customers "undoubtedly paid more than... More →
  • July 12, 2013 - Renewable Heat Incentive Updated - Solar Thermal to have Heavy Support - The Government have today released the Renewable Heat Incentive: The first step to transforming the way we heat our homes. If you are looking to buy a SolarTwin System contact Genfit. "the scheme will be open to anyone in these groups who installed... More →
  • May 27, 2013 - DECC announce they are doubling the RHPP grant for solar thermal from £300 to £600 - Solar Thermal Panels Receive Huge Renewable Heat Premium Payment - Solar Thermal has received a huge boost, it's a great time to buy a Solartwin Product. - Greg Barker tweeted about the scheme - - Big uplift for #RHPP Vouchers to put a shot in the... More →
  • February 14, 2013 - Solartwin DIY reviews - SolarTwin Reviews from Reviewcentre - "Review Centre is a community of real people, just like you, sharing their product and service experiences. - Our community of reviewers are a passionate bunch who want to help you discover what's right for... More →
  • January 17, 2013 - Crackdown on aggresive solar selling - YouGen, a leading consumer body serving the renewable and energy efficiency sectors, is calling for a change in the law after a review by the Office of Fair Trading revealed unscrupulous selling tactics by solar and other energy efficiency... More →

Solar water heating systems = Solar panels + solar energy. Solar thermal: solar power & solar hot water. Photovoltaic (PV) pumped solar heaters. How do solar panels work?

Solar panels. Advantages of solar power. Choosing Which Solar Water Heating Panels. FAQ. RHI Solar.

Questions and Answers for people interested in achieving low and zero carbon homes with the knowledge of solar panels and how they work.

FAQ

 

If this solar factsheet does not fully answer your solar questions, please just ask us here

How can you offer high performance off-grid PV pumped solar water heating technology at a competitive price?

  • Because Solartwin is far simpler than traditional solar water heating.
  • Designing out complexity from solar heating systems means designing away from problems.
  • Minimising hassle and disruption, Solartwin solar water heating usually takes about half a day to fit.
Solartwin is the leading solar thermal innovation to emerge from Britain. Solartwin solar installations take about half the time to fit.
Conventional solar water heating usually requires 3 or more person-days on the job. This is a problem and can mean choosing to have no water overnight. But Solartwin’s offgrid solar panels tends to be fitted faster because they have flexible pipes rather than metal ones. Plus if you do not need to have your hot water cylinder replaced, which is often the case, Solartwin solar heating can normally be fitted in under a day.
The other way we keep cost of solar panels low while keeping quality high is by doing as much as we can together by phone and on the web if you want to buy solar energy or have a solar quote. So we always give you 10% discount for letting us quote for your solar water heating system by phone. Your valuable help in givng us the information we need allows us to get installed solar panel prices to you in a few minutes instead of several hours (at best) comparted to if we were doing solar quotes quotes by car. So this eco efficient solar panel “ecosurvey” means that we can offer you (and the environment) better value for money.
Then you can choose your kind of solar installation for your solar home. Conventional low carbon solar thermal or zero carbon solar heating with Solartwin? (We don’t supply any mains pumped solar products for home use at all).
Will you purchase a full solar install? Or would you prefer a lower cost solar DIY kit?

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You claim low solar water heating system running costs? How does Solartwin save energy compoared to traditional solar?

  • No mains electric bills, thanks to Solartwin’s 100% solar powered (photovoltaically pumped) and therefore zero carbon operation pump. Solartwin=heat+electricity.
  • Solartwin often needs less top-up heating than traditional solar thermal technology, thanks to more hot and less tepid water due to the way hot water is stratified (floated) over cold
  • Rapid fitting, less top-up heating & solar powered pumping = real value, not just to you but also to the environment.

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How big is the main solar hot water panel?

Your solar panel usually looks surprisingly big on the ground, but rather smaller on the roof! The main Solartwin solar water heating panel measures 2.465m x 1.265m x 80mm deep. (approx 8’ 5” x 4’ 5” x 3”).

The solar panel, when fittted normally projects less than 100mm above the roof, so Solartwin solar panels are often treated as “permitted development” by UK planners. The solar panel’s “footprint” with frame is 3.25 sq m. The solar panel’s “aperture” to the sun is 2.8 sq m. Lightweight, weighing 31 kg (empty) or 33 kg (full) a Solartwin solar panel installation rarely requires UK building control. Below is a diagram which illustrates the size of the standard landscape solar panel.

Solartwin size

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So simple? What’s the basic concept behind these solar panels?

Solar Twin Ltd offer simple, technically elegant, double award winning new solar panel technology, which offers you a sustainable, efficient solar home with a difference. Our solar design brief maximises reliability, simplicity, environmental benefits and solar hot water delivery – while minimising capital and running costs for your solar water heating system.

  • This solar panel was invented at Napier University, Edinburgh. It is solar electric (PV) pumped, not mains pumped.
  • Solartwin won a DTI “Smart Award” for its innovative freeze-tolerant solar water heating technology in 1998.
  • In 2003 the solar heating system won again – a “Smart Achievement Award (PDF) ” – this time for commercial success.
  • In 2008 our solar panels were awarded Solar Keymark – Europe’s highest recognition of solar panel quality.

Hidden in Solartwin’s simple but efficient solar panel is our patented heat absorber. This contains our unique flexible solar hot water channels which are the key to our success.

  • Double glazing in front of the solar panel’s absorber surface lets the sun’s heat and light in. The incident solar energy makes it very hot.
  • Daylight runs an “intelligent” and efficient variable speed solar electric PV (photovoltaic) pump.
  • It pumps cold water, via a narrow pipe, from the bottom of your existing hot water cylinder into the solar hot water panel. Here, the water heats up.
  • Thanks to the solar powered pump, your solar hot water, and the free energy it contains, then delivers itself, direct, to the top of the hot water cylinder. That’s it.

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Greenenergy is OK but do your flat plate solar panels look OK?

We think that Solartwin solar panels make a great home improvement! – (installation photos) Inevitably, solar heating roof panels can be visible parts of the outside of a building, so we aim for classic good looks (rather than garish conspicuity!). Solartwin’s slim matt black solar panel frame looks like a big, neat roof window. Optional additional “glazing bars” attached to the front of the solar panel can be of aesthetic value in conservation areas. We now also offer bespoke solar panel frame colour options including brown, cream, blue-grey and deep red.

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What about reliability and maintenance issues in your design of solar water heating systems for domestic use?

  • Solartwin solar panels are a reliable, proven, robust, safe, low maintenance, type of solar water heating.
  • Because Solartwin has a water filled solar panel, it does not need to have antifreeze, so it doees not need an engineer to come to replace the antifreeze every 2-3 years. Regular replacement is a requirement of many solar antifreeze suppliers.
  • Solartwin solar water heating systems come with a 5 year system performance warranty in UK / Ireland. You may need to use appropriate hardness contril such as an ion exchange water softener on your water supply, to validate this warranty.
  • Our solar thermal system contains very few parts and made in UK under ISO 9002 quality management, Solartwin is an intrinsically reliable solar water heating system. Having had the problems of conventional solar heating designed out, Solartwin uses no antifreeze chemicals and frees you from safety concerns about highly pressurised piping, mains voltages and large smashable glass panels or tubes.
  • The solar hot water pipes are robust yet flexible. Made from silicone rubber the deliver bacteriological safety to BS 6920, and take high solar water temperatures too.
  • With Solartwin solar panels for water heating installed, you are not dependent on the mains electricity supply working. Electric power cuts do not make Solartwin solar hot water systems need repressurisation by an engineer since it is a low pressure, off grid technology.
  • The Solartwin solar panel is inherently self-regulating. Going on holiday? You don’t need to invite neighbours in for baths. You can even turn off the main water stopcock if you want.
  • Moving house with your solar panel? No problem. Simply un-install and re-install your solar panel: your warranty is portable!

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Why all this focus as a eco-efficient solar supplier to homes?

  • Because solar water heating is (potentially) a profoundly environmental product, and we want to make it that way.
  • Because our 100% solar electric pumping system eliminates the typical 20% environmental penalty associated with using mains electricity to run solar heating pumps and controls.

The Solartwin solar water heating system is a sustainable and safe solar thermal technology because of an exceptionally safe combination of:

  • Zero carbon operation
  • Light-weight panels
  • Non-boiling in normal operation
  • Low voltage
  • Low pressure
  • Low Legionella risk

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CO2 saving from solar panels? Really? Where’s the hard evidence of this 20% penalty for older solar water heating designs?

  • A recent UK government-funded study of eight solar water heating systems confirmed what has long been suspected: that the environmental benefits of solar can be substantially improved by eliminating mains electricity by using PV pumping. (Side by side testing of eight solar water heating systems 2001 DTI/Pub URN 01/1292 (PDF) )
  • In this study, flat plate solar hot water systems negated an average of 17% of their potential global warming benefits (i.e. CO2 savings) by using mains electricity.
  • For partial-vacuum tubes (“solar tubes” “evacuated tubes” or “vacuum tubes”), their loss averaged even higher, at 23%.
  • In other words, if you run mains-powered solar water heating systems for ten years, its electricity consumption deletes its CO2 saving by about two years.

Solartwin’s environment-centred solar water heating design brief specifies a solar electric (PV) pump. So your CO2 savings won’t retreat two steps after advancing ten. Rather than focus on making the most efficient solar panels, at all costs, since we reckon that these would require lots of resources to make and too much electricity to operate we are deliberately seeking to make the most eco-efficent solar panels as part of our “big picture approach to design”.

  • Per year, a Solartwin solar water heating system will save about a quarter of a tonne of CO2 if mains gas is the guel which you displace. The figure will be higher if bottled gas, oil, coal or electricity are saved instead by your using solar.
  • Solartwin’s “carbon breakeven” (ie manufacture carbon budget against savings from running the solar panel) is around 18 months according to detailed analyses carried out by Bath University. Again this timeframe assumes that mains gas is displaced by solar panels. It would be even shorter for other fuels listed above.

Besides being a leading solar thermal technology on the issue of zero carbon clawback in operation, we also aim to lead the global solar thermal industry in tems of carbon breakeven time because our technology, as a whole, is lightweight and it is designed as sustainably as possible and with the lowest carbon footpriint as we can reasonably achieve.

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Any other environmental issues on your solar panel technology, apart from the benefits of using solar energy for pumping?

Yes, our solar technology and ways of working are environment-centred. For example:

  • goodbye to antifreeze chemicals in the solar pipes
  • you usually keep your cylinder: waste less when you install solar heating
  • uses “green” hydro-aluminium for the solar panels
  • lightweight = less embodied energy in your solar panel
  • hotter solar water = less top up heat
  • energy-efficient microbore solar hot water pipes
  • phone, not car surveys save CO2 when you buy solar thermal.

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What is so efficient, green and simple about Solartwin solar panels’ innovations?

Redesigned from scratch, this solar panel’s freeze-tolerant technology is the key to its simplicity. Solartwin’s flexible thermally conductive pipes actually freeze solid in winter without cracking. In sun, they thaw out fast. This “Holy Grail” of our solar panel makes Solartwin unique, by:

  • Eliminating most of the gadgetry, plumbing, antifreeze, unreliability & maintenance inherent in traditional solar water heating systems. (Antifreeze is four to six tmes as stiicky (viscous) as water so it needs more energy to pump it (which is why we can use a 5 watt solar electric panel to power our pump. Conventional solar needs a much larger, say 25 watt pump to pump antifreeze if it were to use PV pumping at all.)
  • Usually delivering hotter water whether it is sunny or overcast, and earlier in the day.
  • This helps towards the solar panel creating your zero carbon house.
So the technical cascade, as a summary of our solar panel design approach, is this:
  1. Flexible pipes lead to Solartwin’s water-filled (not antifreeze-filled) solar panels. With Solartwin, this water may need to have its hardness controlled properly or the panels may scale up. Domestic limescale controi is an established and proven technology so preventing scaling is not a problem. While our silicone rubber pipe is not as fast a conductor of heat as metal in old solar panels, the wall of our pipes is only two millimetres thick, plus ithas a large surface area, so it offers very little thermal resistance in practice, even at high sinlight levels.
  2. On the other hand of the design tradeoff, antifreeze in conventional solar panels usually needs replacing every few years. It can degrade over time. Replacement can be expensive and it is a hassle to organise. We view antifreeze as an avoidable burden of maintenance upon solar panels.
  3. Some chemical solar panel antifreezes can also coagulate and block conventional panels at high (stagnation) temperatures.
  4. And if solar heating antifreeze degrades or leaks or boils out, and is then replaced with water, as sometimes happens, the unprotected metal solar panels may crack in cold weather when they freeze, requiring them to be replaced with new solar panels. Sometimes even a compete new solar water heating system. In our experience, this tends to be Solartwin, because our solar panels are freeze tolerant
  5. As a major plus, once it has collected the solar energy as heat contained in water, Solartwin’s solar panel carries and conducts heat rather better than antifreeze can. The fact that water is about six times less sticky (viscous) also helps. For example, it means that concentional solar hot water heating systems can have problems if air bubbles do not get expelled from their solar panel circuits, to the extent that special new solar cyclone devices for spinning these bubbles out have now been developed to prevent them from reducing conventional solar pumps from cavitating – which causes them to work at reduced or even zero capacity.
  6. Besides getting rid of freezing problems in metal solar panels, one major benefif of having water-filled solar panels is that they allow you to use less energy on pumping. The Solartwin approach of using not antifreeze but (much less sticky) water in our solar panels means that conventional solar water heating’s energy burning 20-50 Watt pumps can be dispensed with. They can replaced with Solartwin’s miniature, well engineered, 5 Watt solar water pump based on a brushelss DC motor and a diaphragm pump head. This is always run on solar photovoltaic electrricity, solar power that is generated on site. That’s the “zero carbon” solar panel operation innovation.
So, Solartwin’s environmentally efficient solar heating panels have been redesigned from scratch, as has the whole solar water heating system connected to it. The solar hot water system design cascade interlinks: starting with stretchy, clean silicone rubber, to a freeze tolerant solar panel, to using water as a heat transfer fluid, to a low energy pump to it being powered by solar electricity. Design out the problems is our approach.
Solar heating efficiency – at a whole solar system level – is what matters to us. Becaose of this big picture approach, as a solar design company, we are not simply trying to maximise the efficiency of any one particular individual solar thermal system component, if this happens at the expense of the overall efficiency of the solar system, when considered together. So all the Solartwin solar water heating system components are interdependent with each other and are optimised, by careful design, to work with each other.
And’s that’s we don’t mix and match Solartwin solar heating components with kit from other solar water heating systems. (The one exception is from the solar pump controller, which we have designed to be generic, across conventional solar water heating systems in the hope that conventional solarthermal will eventually go green.
I hope that you have found this cascade explanation of how solar panel innovation at Solartwin operates to simplify (and greenify) our solar water heating system to be interesting – and not too techy – but – If you want more techical info on Solarwin solar panels, just go here.

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Hotter solar water, how?

Because of Solartwin’s variable speed single pass pumping, our solar panel coatings, no heat exchangers and stratified (top down) hot water storage…

  • Variable speed solar PV pumping is more accurate than traditional on-off control. Solartwin measures and adjusts to daylight as dull as 10-20%, so water stays longer in the panel, heating up better.
  • Our solar panel coatings maximise heat gain up to around 70C, while usually giving boil-protection when you are away. Harvesting 95% (+/- 3%) of ordinary daylight plus non-visible infrared, our coatings don’t need hot days nor bright days to catch energy effectively.
  • No heat exchangers. Indirect solar heats water via a heat exchanger at the bottom of a costly new cylinder. But solar heat exchangers impose system inefficiencies: they rely on cooling in order to operate. Some partially evacuated tube (solar tube / evacuated tube) systems have second heat exchangers on the roof.
  • Stratification = Top down heat. Solartwin delivers solar heated water direct to the top your existing cylinder, maximising temperature by floating (stratifying) it, unmixed, on cooler water below. So when you open your tap, Solartwin solar hot water arrives, first. And it gets hot earlier in the day.

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So what is the specification of your solar panels systems?

A standard Solartwin solar panel installation supersedes traditional solar thermal technology in several ways. It gives direct solar water heating from a patented, freeze tolerant, double glazed flat plate with a variable low speed photovoltaic circulation, using no heat exchanger. (Earlier solar thermal generations used indirect antifreeze circuits, heat exchangers, mains powered control, high speed pumping plus single or double glazed collectors such as metal back-piped flat plates or partial-vacuum tubes / evacuated tube solar panels.)

As for originality the Solartwin solar panels technology is the main solar thermal innovation to emergy from the British Isles. As a technical specification summery, the Solartwin solar water heating system can be described like this:
  • Solar collector geometry – flat plate solar panel
  • Main materials – polymers and metals
  • Solar heat transfer fluid – water
  • Freeze protection – flexible silicone polymer pipe in solar panel (and to and from the panel).
  • Solar circulation pump energy from – PV
  • Solar circulation flow control – variable speed solar pump plus solar controller
  • Max flow speed – ultra low flow, 0.25 litres / sqm / min
  • Heat exchanger: solar/store? – No, usually direct to top of store
  • Solar water store stratification – excellent
  • Solar absorber coating – matt black (to allow LW IR emission)
  • Solar water overheat control – heat export (pump on) if store >65C
  • Solar plumbing pressures always low. Open vented.

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What are these new solar panels made of?

The main metal in the solar panels is hydro-electrically made aluminium, with a lower environmental impact than aluminium made using fossil fuel. For durability, external screws / bolts are stainless steel. The absorber coatings are matt black. Double glazing is UV-stable polycarbonate. Double, rather than single glazing optimises winter performance. Insulation is zero-ODP pentane-blown rigid foam.

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The solar pump specification?

The 11 volt (peak) photovoltaic panel powers a self-regulating, variable speed, long life brushless DC motor. This drives Solartwin’s positive displacement pump. Valves in it stop “reverse thermosyphon” at night, and a bypass valve protects against “frozen by day” conditions. The fact that the solar punp is low voltage makes DIY solar hot water installations safer and easier in comparison with solar panel installations which need to connected to mains elecrticity in order to get them to work.

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Flexible solar water pipes.

Solartwin’s freeze-tolerant, corrosion-resistant solar pipes are made of silicone rubber. Its extreme temperature tolerance range is: -60C to +200C! This silicone is also used, for hygiene reasons, for milk pipes in dairies. Its material conforms to the requirements of UK-WRAS for hot water and European Extraction Testing Regs 90/129/EC (BGVV XXI) for food contact, and USA FDA 21 CFR 177.2600 for food contact. That’s why it is an ideal solar panel making material.

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Energy Saving… I’m here to save the environment and save energy. How big is Solartwin’s solar energy output?

  • One Solartwin solar panel typically heats a normal 120 litre hot water cylinder to 50-60C on a sunny March or Sept. day ( 60-80C in summer). Independently tested, a Solartwin solar heating system delivered 1000 kWh (3.6 GJ) of clean green energy as solar hot water a year in UK. It saves far more bought-in energy.
  • As for energy efficiency, the solar panel peak power output is 1.6 kW, similar to an immersion heater.
  • These solar energy figures are derived from several reports including EN 12975 tests in Austria under Europe’s Solar Keymark Scheme: assuring you the best solar panels when it comes to quality.

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Solartwin solar heating systems aim to offer the best quality, convenience and design under the sun.

For speed, and for the sake of the environment, Solartwin offer feasibility checks and fixed price solar quotes by phone.
Unique in the world, Solartwin's phone survey now also uses online aerial photographs of your roof in most urban areas!

Unlike most solar surveys, our instant surveys and quotes are completely free and with no obligation.
Click here to request a survey

Or Call us on

0344 567 9032

Domestic Renewable Heat Incentive Released

Solar Thermal has got the great government funding through the Domestic RHI which it deserves! Solartwin Solar Thermal panels have just become not only a cost cutting and very green option to heat your water but now you will receive additional funding too! The Domestic RHI rates – Released April 2014 Ofgem have produced a […]

Read More | Archives

Notice to Solartwin customers – Letter’s from Stenfield & Co

A number of Solar Twin Ltd customers have been in touch this week to query a letter they have received from legal firm Stenfield & Co. The content relates to Solar Twin Ltd’s liquidation, and claims that customers “undoubtedly paid more than you should have and it is highly likely that you will have been […]

Read More | Archives

Renewable Heat Incentive Updated – Solar Thermal to have Heavy Support

The Government have today released the Renewable Heat Incentive: The first step to transforming the way we heat our homes. If you are looking to buy a SolarTwin System contact Genfit. “the scheme will be open to anyone in these groups who installed an eligible technology since 15th July 2009” so if you have a […]

Read More | Archives

DECC announce they are doubling the RHPP grant for solar thermal from £300 to £600

Solar Thermal Panels Receive Huge Renewable Heat Premium Payment Solar Thermal has received a huge boost, it’s a great time to buy a Solartwin Product. Greg Barker tweeted about the scheme – Big uplift for #RHPP Vouchers to put a shot in the arm of the market ahead of full Domestic #RHI tinyurl.com/ktxz3o2 — Greg […]

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Solartwin DIY reviews

SolarTwin Reviews from Reviewcentre “Review Centre is a community of real people, just like you, sharing their product and service experiences. Our community of reviewers are a passionate bunch who want to help you discover what’s right for you.” (Review Centre) We are well rated on review centre, this shows the excellent product quality of […]

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