Solar Panels

[porca misèria]

Was thinking earlier today about temporary collection / storage of heat to aid heat pump efficiency (and reducing scale of eathworks/borehole size to still have a functional system). Hadn't thought about the much longer term (seasonal storage). How efficient would boreholes be though (and how costly), wouldn't you need a really exxtensive array of them to have any chance of properly transferring the heat to the ground? What about a very large underground tank - concrete lined small swimming pool type affair - you could get away with a lot less pipework as a relatively short length in the water and thermal circulation of the water should be very efficient at extrating maximum heat from the heat collectors.

Sounds like something Heath Robinson would be proud of!

If it's just a normal house for a small number of people with a sunny, south-facing roof, solar PV is going to be the more efficient way to harvest the sun. Not moment-by-moment, but overall.

Hot water becomes more efficient if you've got a use for lots and lots of it. Or sometimes in adverse circumstances, like where too much shade at the wrong time&place clobbers PV performance but only slightly impairs water heating.

[fluffy666]

[quote name=Oh Well ' timestamp='1318669131' post='3149185]

the inverters will fail.

you will need toclean the panels twice a year.

your roff will leak as the fix through tiles

the feed intarrif will be scrapped as the government runs out of money

anything else?

Actually, we are in the process of getting the panels..

The kit and installation is guaranteed for 5 years (minimum, varies between 5 and 25 years), so immediate inverter failure is not a problem.

For panel cleaning, we have this thing called 'rain'.

We haven't had a problem with the roof leaking after the boiler was moved inside and a new chimney put in.

FIT comes directly from the energy companies.

You missed out: The moral dilemma of knowing on one hand that rooftop solar isn't going to make much difference to either GHG emissions or national energy security.. but on the other that they do give a very good ROI, and if we start having real problems with electric grid reliability in the near future, having the panels in place would make going off grid that much easier.

[bkkandrew]

The truth is that a one-size-fits-all with renewable energy is foolish. A good combination of solar H/W, solar aircon (out here), PV panels to suit the local climate and insolation period and other devices can make the most cost-effective solution.

For example, on a solarisation job of a few thousand telco towers we cust down the cost by 30% when discovering that most of the electrical useage was aircons to keep the kit cool. Swapping these for solar reduced the bill by 30% even thought they were getting new aircons.

There is no alternative really to doing an energy audit of your premises and making recommendations from there.

[Kurt Barlow]

Was thinking earlier today about temporary collection / storage of heat to aid heat pump efficiency (and reducing scale of eathworks/borehole size to still have a functional system). Hadn't thought about the much longer term (seasonal storage). How efficient would boreholes be though (and how costly), wouldn't you need a really exxtensive array of them to have any chance of properly transferring the heat to the ground? What about a very large underground tank - concrete lined small swimming pool type affair - you could get away with a lot less pipework as a relatively short length in the water and thermal circulation of the water should be very efficient at extrating maximum heat from the heat collectors.

Efficiency of ground storage will depend on the type of soil, water table etc. Preheating soil would probably double COP so halve electricity consumption of heat pump. With these set up there is an obvious economy of scale so better for larger houses.

What I would do is have the borehole under the patio and put 12 inches of polyurethyene in as a thermal cap.

I estimated a few months back that materials for such a system would come to about £20K

The solar array was 6 x 30 tube (58mm) solar panels. These would harvest about 22000 kwh a year £3000

A 300 litre water storage cylinder £500

Controller £130

Valves £200

Radiator to act as buffer £100

Pressure kit £100

Pipework and fittings £200

Heat pump, Pipework £6K

Underfloor heating £2K

Borehole - £4K

Labour - £4K

With this system you get all your heating and hot water for less than £200, less if the heat pump is run on economy 7.

[Rare Bear]

One possible way to utilise this is to dump the surplus down a vertical borehole which is also the heat source for a Ground source heat pump. Its pretty straight fwd to design a system that provides hot water year round and dumps the surplus in a borehole which then massively improves the COP of the heat pump.

Good thinking. Is it your own idea or has it been around for a while?

[Kurt Barlow]

Good thinking. Is it your own idea or has it been around for a while?

I have seen a few variations on the idea on bodgers websites. I Havent seen a design exactly like I would put in.which is designed to give year round hot water and dump summer surpluses into the bore hole.

I would also add in a couple of radiators to allow direct bleed off of solar heat when its in surplus and there is heating demand (sunny winters day for example).

[Rare Bear]

I have seen a few variations on the idea on bodgers websites. I Havent seen a design exactly like I would put in.which is designed to give year round hot water and dump summer surpluses into the bore hole.

I would also add in a couple of radiators to allow direct bleed off of solar heat when its in surplus and there is heating demand (sunny winters day for example).

I did once consider building a house with a big, as in swimming pool big insulated tank as a heat store. At the time I had a site beside an old mill dam, average flow i cubic metre per scond and a 6 metre drop. My thought was to stick in a hydro plant and store the spare energy as heat for the cold days when the river flow was bad.

[Kurt Barlow]

I did once consider building a house with a big, as in swimming pool big insulated tank as a heat store. At the time I had a site beside an old mill dam, average flow i cubic metre per scond and a 6 metre drop. My thought was to stick in a hydro plant and store the spare energy as heat for the cold days when the river flow was bad.

Nice - stand to be corrected but;

1000L x 6 x 9.7 (gravitational constant) x 0.7 (efficiency of turbine) = 40.7KW. With that sort of potential I'd be looking at export rather than conversion to heat.

[Rare Bear]

Nice - stand to be corrected but;

1000L x 6 x 9.7 (gravitational constant) x 0.7 (efficiency of turbine) = 40.7KW. With that sort of potential I'd be looking at export rather than conversion to heat.

The snag with export was that at that time in Ireland the ESB, the Electricity Supply Board, would only pay 25% of what they charged for electricity. Even so, the idea of a house there with the water turbine was attractive but as Ireland was well and truly screwed in the mid 80's I left there.