The first PV + thermal (PVT) solar hybrid panel was developed in Germany in 2007/8 and shown to the trade at Intersolar Germany. At that time, the cost of PV panels was very high, but the Munich based manufacture i later visited had developed a way useing automotive robot bonding, to bond a thermal water panel to the PV frame free glass panel.
Since that time, many other PV and flat plate solar panel manufactures have developed there own idea of PVT, including a UK company developing a PVT evacuated tube collector.
The following pages, PDF files and pictures will open up the debate that is going on across the world, from China to the USA, from the UK to Europe and beyond and what the future of PVT holds in the future.
The flat pack thermal store design with material costs I developed with my USA partner in 2013, was shared with the founder of Sirac in Sth Africa in 2014. A royality agreement followed with Solar Speedflex exporting the helical heat exchanger stainless steel coils to Sirac since 2014, which has transformed there business with no competition to copy from them.Now opening similer oppotunities in many other countries, who are looking to move away from transporting large commercial hot water steel tanks full of air.
The idea to couple together a solar PV panel with a solar thermal panel into a PVT solar panel was to circulate cold water through the back of the PV panel to cool it down below 26c with a pre heat warm water benefit of up to 30c.
The figure 26c is the temperature that all the worlds’ solar PV panel manufactures use to find the efficiency of each PV panel they produce, which is an indoor controlled certified test.
It’s a worldwide proven fact that once temperature of the solar cells start to increase above the 26c, the efficiency starts to fall the hotter the glass becomes.
The German manufacture produced such figures to demonstrate this and it’s through that company others have followed, with around 56 companies across Europe promoting such a PVT hybrid today.
The drop box down load demonstrates this in a power point presentation as a PDF, where it’s been proven that the glass encapsulating solar cells can heat up above 60c in air temperatures of 32c with clear blue skies. At this temperature the efficiency of the solar PV panel drops by 0.05% for every 1 degree rise above 26c. Even in a very cold air temperature, glass solar panels can still heat up above 26c.
The concept behind the placing of a solar thermal panel behind a glass PV panel is to cool the back of the solar cells to maintain the panels test efficiency, as has been sold to its purchasing clients.
Unfortunately, the PV panel manufactures are not interested, as they see the increased cost and delay in the installation of PV only as adding a cost to the sale of their PV panels. This lack of knowledge and working experience of much wider use of solar thermal panels is why there is little interest to date, but that is soon to change.
Then you have the solar thermal industry, that is fighting solar PV “to retain a solar water heating industry” but instead of looking beyond the mass produced flat plate solar water heating collectors that they see as only needing the glass changed to a PV glass, that’s where all the problem begin.
I hope to break all this down over the next few pages with facts, pictures and PDF files written up years ago, along with you tube videos’
Up until 2016, all PVT solar panels used the now cheaper mass volume produced glass PV panels, to attach a solar thermal panel to the back.
The far right hand picture uses a slim metal plate panel that is filled with a water/glycol mix, as a retrofit to any brand of solar PV. Sundrum solar in the USA uses a similar idea, so they do not need to buy in a solar panel of a brand a potential buyer does not like.
The 2nd picture from the right hand side is where a standard copper flat plate absorber has been fitted to a brand of solar PV panel and sold together as a PVT panel.
The 3rd picture from the right, is the only company (UK) who had the idea to imbed solar PV cells onto the copper heat pipe sealed inside an evacuated tube (This UK company managed to secure over €1 million from the EU and a further £350,000 from DECC in the UK)
The picture on the far left is the back of my NEW glass free poly/mono cell PV framed panels encapsulated with a Du-pont material from the USA to provide a 100% guaranteed water tight seal, with a backing of aluminium.
To this NEW exclusive glass free panel, we retrofit our low cost light weight aluminium U channel thermal absorber with inset silicone tubing which the water will flow through to cool the back.
What is very different between the NEW Thermaltricity PVT solar hybrid panels is that the back of the glass free PV panel transfers the heat from the front that is facing the sun, to the back. The backing is a heat sink to which our thermaltricity panel absorbs 100% of this waste energy (watch the you tube video assembly to a then glass PV panel of 250 watts
Producing an affordable two part PVT solar panel has taken 2.5 years to develop as a PVT system, because the selling of a PVT panel on its own does not end there.
This is the final part of the section that relates to the PVT solar panel choices, to be followed by WHAT ARE THE SYSTEM OPTIONS to maximise the use of both the generated DC electricity as well as the heated water to 30c
What was proven in the early days of selling PVT was to use the heated water passed across the back of the PV panel to heat a swimming pool.
What was proven beyond any doubt, is that when you have a large water store volume open to gravity, with the right amount of PVT panels that over a 8 hr day during the summer months in the Northern climate, that the pool water volume would never over heat above 30c.
The sizing of the water storage tank and the plumbing of the system, i will present after completing this part of the facts.
During recent tests between glass PV panels with a plastic film backing and my NEW glass free PV panels with the aluminium backing, the temperatures I recorded both at the same position to the sun, on a day of clear blue sky in the South of England in June 2017, was to show that the glass maximum temperature reached 62.4c while the glass free reached 64.4c