Friday, February 11, 2011

Photovoltaic and Solar thermal - Solimpeks

1102-2011 : I see that PVT - Photovoltaic and Solar thermal is coming one step closer with this Volther product from Solimpeks. The Building Green blog does a good write up of them:
http://www.buildinggreen.com/live/index.cfm/2010/6/10/A-CuttingEdge-Hybrid-SolarThermalPV-Collector-from-Turkey
and the Green Optimistic does a good write up too with a better picture:
http://www.greenoptimistic.com/2010/08/31/volther-hybrid-solar-solimpeks/
The document from Solimpeks themselves is:
http://www.solimpeks.com/File/voltherhybridcollectors.pdf
I want one!!! Or a few..!
At the moment, I am not aware of one that is on the market in the UK, although the company EcoMerchant may be a source. http://www.ecomerchant.co.uk/ and then click in Products for 'Solar Thermal'. There are two types, the PowerVolt and the PowerTherm. Each of them majors on one technology or the other according to name.

  • Powertherm would be better on very small roofs where you judge that thermal is important. The panels have a gloss top and I guess, an insulated back. The thermal part of these would work longer into the equinox and winter.
  • PowerVolt - On a larger roof where you can go up to 20 square metres or more, you would not need such a large amount of Thermal, so you would use PowerVolt, maximise your PV harvest and then take advantage of the large thermal capture that would come from this only during the summer (no insulation or glass cover).

Liquid cooled PV is ideal if such a thing is available and MCS approved, imagine having 20-28 sqm of PV, and all that being thermal too. A bit of a plumbing nightmare, but if installed at the time of new build would be incredibly effective. The PV would have increased production (ours always does better if a cold north wind blowing on sunny day) and the same area of thermal instead of our puny 4 sqm. However, we do quite well by using the greenhouse/ solar cooker effect.
   From my point of view (being interested in Solar Interseasonal charging) they could be ideal because in summer, most normal tank based systems reach stasis quickly. 20 sqm of thermal panels would reach stasis extremely quickly if the only store is a 300 litre tank. The earth charging process doesn't suffer from stasis as the thermal capacity of the boreholes is close to infinite, and there will always be a delta-T that is beneficial. Thus the PV panels will be well cooled in summer no matter how hot the weather because the liquid coming up is sure to be cool. Imagine how much heat would go down if we had much more than our present 4sqm. Without the glassy sunboxes over them one would get little capture in winter, but the summer storage would be so comparably colossal that this would compensate. I have a temperature gauge on my PV panels and know that their surface temperature goes well above 50 degs C in summer, in fact, they go off the scale! They need cooling!
[Many thanks to David Hill of Carbon Legacy for alerting me to this and to Walthamstow.]
He also points out to me that the new replacement for Walthamstow Fire Station will have 188 sqm of these panels, giving them over 22 megawatt hours of electricity and over 76 megawatt hours of heat, all to be buried in the ground, to be recovered by a heat pump. It's wonderful to be finding something that is so directly and confidently doing what I have been trying to do, in my lonely furrow.

4 comments:

  1. Hi David,

    These types of panels are something that I have investigated a number of times over the last couple of years (commonly known as PVT (photovotaic - thermal)).. As in the way you have stated, the benefit of these lies with solar recharging. A met with a representative from a canadian manufacturer of these panels only two weeks ago in fact. Obviously the financial benefit going forward would mean that they would attract both the FiT and the RHI. I hear claims that when used for heating domestic hot water that they can increase the electricity yield by 15-25%. I am not so sure as when you heat the DHW tank then there will be long periods where the circulation behind the panels must be around or above the 60degC mark in order for a heat transfer to be effected to the tank - and at that temperature that would be a detriment to pv efficiency.. however when connected to the ground array, great efficicny gains could be had... but i do disagree with your claim of infinite thermal capacity of the boreholes.. This is not true and with a continually injecting heat into the ground through the summer will cause the temperature to rise. This is just simply an energy balancing act. In the same way that we size boreholes for cooling of buildings (i,e, dumping air con heat into the ground) we would have to size the borehole for the solar heat input. (obviously with 4sqm vs 100m of borehole, i'm sure we would be well within the margins!)

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  2. I said 'close to infinite' assuming that if you are an adventurous mole you could eventually tunnel all the way to the campus.... but I realise that there is a realistic range of about 3.5 metres for recharging, and if you over heat, it will eventually escape before winter comes and you have time to get it back. This reveals one of the benefits of a Twin Borehole that hadnt been apparent before, because I must have a sort of warm zone between them that helps with solar recharging.
    I heard that with the Anneberg project, they intended to heat the ground to about 37º and thus be able to get heat back without needing a heat pump to convert... but someone (may have been you) told me that this hadnt worked as well as hoped, in that the system losses were too high - losses to the infinite ground, and in the pipes. So I am confident in the use of our now-highly-tuned heat pump to get the heat back and will be happy if we get the ground up to 16 or 17 next summer.

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  3. With no solar recharging, the twin holes being close to each other has the reverse effect, it becomes a big problem because external warmth cannot penetrate that zone easily so it is more chilled than the outer part of the two rings.

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  4. What a fantastic initiative! Great to hear about it! Solar Photovoltaic PV Panel

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