Thermodynamic solar/anytime panels

Well, I think this is the same "technology", if not even the same product, that was widely publicised some time ago, with the same sales arguments: solar panel that works at nights, astonishing savings, bla, bla, bla.

I have had a look at their (http://lvprenewables.ie/) promotional video, and it has simply confirmed my suspicion: it's nothing else than a regular hot water tank with an added small water to water heat pump. The same concept that fridges and freezers use, but obviously operating on a reverse cycle. So, it can consume good amounts of electricity, because heating water using a heat pump can be much more efficient than doing so with a simple resistor (passing electricity through a rod and heating via Joule effect).

A heat pump efficiency can be four or five times more efficient than the Joule effect: that is, for every electrical kilowatt spent on the heat pump, you could theoretically get four or five thermal kilowatts, instead of just one with Joule effect. Heat pumps operation and physical principles are well explained on the Internet, so I'll avoid doing it here.

The problem is the efficiency of heat pumps largely depend on the temperature difference between what is called the "cold spot" (in this example, the environment) and the "hot spot" (the heated water in the tank). The larger the gap, the lower the efficiency. So a heat pump, like a fridge, can work with no need for external devices, it all depends on which are the cold and hot spots.

So, back to the advertised system. What's the point of it, and where do the magic comes, or what is the solar panel good for? In this system, the cold spot is the cold water that comes into the house via the pipes, the cold tap water. The hot spot is the water in the tank. Ans the solar panel on the roof is just there to help preheat the incoming (cold) tap water, to improve the heat pump efficiency.

Depending on the environmental conditions, weather, sun radiation and panel size and orientation, the incoming cold water that comes at (lets say) 10 ºC is circulated along the solar panel, that during the day can be hotter than the water itself, giving some of the energy to the incoming water, and raising its temperature. How much? During a sunny summer afternoon, by quite a lot. At nights, nothing, and during much of the 6 to 9 month long irish winter, it can even be detrimental (you won't want to circulate water at 10 ºC through the panel even during the day, if outside temperature is 5º C and sun radiation is so low, due to the sun being low on the horizon and dense clouds, that no gain can be realized from the sun).

So, the system works day and night, because the control logic will turn the heap pump whenever necessary to make water in the tank be at the configured temperature. The computer will pump water to the roof panel it it thinks this can make water raise its temperature, and it's expected to stop pumping when no heat gains can be obtained. During optimal times of the year, the heat pump will work less hours, and during winter, and depending on hot water usage, it could be on 24 hours a day (the webpage video says it only drains about 400 W when on, so from this power rating it's safe to think that during winter, the heat pump will be on most of the time). And don't rule out the possibility that a simple resistor (like those found in traditional hot water tanks heated by electricity) is used as a backup when the heat pump can't simple cope with the demand.

So, is this product the marvel they are trying to sell us? In no way, and for the typical irish weather, I don't think it is worth the expense. Ireland has a difficult weather for solar power (either PV or thermal), because its weather doesn't let too much energy arrive to the ground, and temperatures can be very low (regarding system efficiency) for things like that to be of real use.

The idea of using a system like this to heat a typical irish detached home makes me simply laugh, especially those homes with more than room for improvements in insulation. Please remember, that the amount of energy a square meter on the earth can receive during the most clear sunny days of summer at equatorian latitudes is around 1000 W/sq.m. If the sun is not at a 90º angle (solar noon at equator during summer), less energy arrives to the ground. If there is any mist, less energy. Clouds absorb huge amounts of the incoming sun energy (the same way clouds make heat stay close to the ground, and that's why cloudy nights are usually much warmer than clear ones). And then, technology has its limits, so a high vacuum thermal solar panel can have a gathering efficiency around 80% of the incoming energy, but it also has losses (the panel heats, but also radiates heat, and has other thermal losses, the colder the environment, the higher).

So, if you do the math, this wonder product it's just a salesperson speech trying to convince people to invest in some sort of marvel that, for the specifics of Ireland, simply won't fly. For the country of origin of the panels (seems to be Portugal, at least they seem to be made there), it can be interesting (very mild weather all year, and lots of sunny hours all year long). For Ireland, it's a no go. Save your money and invest in similar technology, without the added (and unnecessary burden) of the solar panel. A water to water heat pump that is preheated using low depth geothermics (horizontal runs of plastics pipes about 2 meters deeps on your backyard) is much more efficient, but can be expensive (excavation cost) or not possible at all (unavailability of enough space).

Renewables are an exciting business, but for the time being there are too many snake oil sellers out there, and customer could make the wrong choice, spend a lot on installation, and then incur in high operational costs once they realize the system is not what they were really sold.

PS: please excuse me, because it's clear that I'm not a native english speaker/writer, and some expressions / technical terms could be wrong, as I don't know yet the equivalents in english of those I know in spanish.

Sent a query to LPC Renewables and got a ring back very promptly. The guy who rang (Richard I think) basically said I was better sticking with condensing boiler in my case. No hard sell at all, even though we are planning to knock most of the house and rebuild so perfect time to invest in a new system he still recommended sticking with old system and loads of insulation

Buzzbarr wrote: »

I was thinking about getting thermodynamic system too. Why did they advise you not to get it? What is your predicted hotwater useage if you went ahead with the system.

Not quite sure, they rang at a bad time. Asked was it a new build. It is almost, only keeping 3 bedrooms in original concrete built cottage and adding about 150sqm. Original cottage will be externally insulated and new build will be insulated to the highest spec budget will allow.

Sounds like a great system but now think airtightness may be an issue, particularly in my case with old cottage.

Finished the conversation saying I'd do more research and get back to them in the new year.

I also want to look into payback period and maintenance costs, my architect thinks this may be an issue.

BlondieR wrote: »

We are looking at these too and it all sounds a little too good to be true. Most threads I read shift to technical specifics of heating requirements, panel efficiency,COP etc..... Does anyone have these panels for space/central heating & do they work?

I have also heard of what has been quoted to me as "solar rads" - efficient radiators that only have 0.6l of water, which can be used to retrofit a house for this system or save the need for underfloor heating + screed in a new build. I'm having a little trouble sourcing them online, are they simply referring to alu rads??

There is another thread here somewhere asking for actual electricity bills from people who have thermodynamic panels. Until I see a meter readings here from someone who has more than 1 post, I remain sceptical.

Generally, using solar to heat your home is a complete mismatch. It is good for heating water in the summer time when your heating is (or should be) off.

The principle of rads that can work at low temperatures have some benefits. However, underfloor heating works with ground source heat pumps because heat is stored in the floor and released over a long period. You don't get that benefit from low temperature or fan-assisted rads of any sort. So your GSHP can't really benefit as much from low cost off-peak electricity.

Thanks for the replies folks, I agree Quentin and the fact that nobody is coming forward with actuals is making me sceptical. If these Thermo panels are so wonderful, why are people not shouting it from the rooftops??

While the science can tell us what a panel could, would & should do, the fact remains that we live in homes not labs and nobody seems to be able to confirm what they actually do.

Back to the drawing board I guess but thanks guys

I fitted the system 2years ago, during 9 weeks of summer we have 11 irish students staying with us, we are a family of 5 , 2 adults and 3 kids, the system supplies all our hot water (not central heating) 1 panel on the roof and a 260ltr tank, ok its slightly slower in winter because how cold the water is but it still heats, every morning we have a full tank of water at 52deg , i bought a meter of OWL to view our electricty usage on average between .5 and .9 kw per hour, thats inc fridge and freezer and other items (tv,upc playstation ) left on standby. the system works for us as we were 100% depending on oil.