Solar Panels - verifying the numbers

Surely this only works for cooling. The outside air is normally going to be colder than the inside air so this is a cheaper way to cool the inside.

It is never going to work for heating up a house (except in some very extreme outside conditions that I think we can ignore)

tim

And which way are they pumping? Outside heat in or inside heat out? B-)

air source works, but its limited both in efficiency and in power output.

Makes a lot of sense in cities though where there is a huge spill of thermal energy from the activity - transport etc.

Aye, and there's the rub.

Ground source is far more useful as teh overall land temperature varies less.

The best approach on a new build is to use the ground under the house, and the plot..pumping heat into it in summer using the system as aircon, and out again in winter using a heat pump.

Many already in operation. Clue: reverse the system.

I worked in an office (UK) which was perfectly adequately heated with such a system.

Chris

I dont think you understand what a heat pump is. Thats like saying a fridge only works if the room is at -5C..

Air source is supposed to be OK down to a few deg.

There is a limit to what you can take out as the heat you remove from the ground (in winter) is replenished by conduction from adjacent ground (it's not geothermal).

Also the capital cost is gonna be lots more, I'd of thought.

Thanks to whoever posted that link to

Yes, I'm a little unclear as to what exactly the objections are to nuclear power generation. I watched that BBC programme last week "How to Build a Nuclear Submarine". The people of Barrow-in-Furness where the things were being built had no fear of the nuclear angle. They just said that it was something they had lived with for many many years. In the same vein as a similar prog that I saw a few months ago about the biggest (U.S.) nuclear sub in the world, just a few kilos of the enriched uranium fuel, would run the thing for 25 years. In fact, I think it said that the American one was commissioned sometime in the 80s, and had never been refueled so far. The naval nuclear engineer responsible for the commissioning of the RN sub's reactor, said on the BBC prog that although the exact details of output were classified, when running at full chat, it would be enough to power a town the size of Portsmouth. I can see that there is potentially an issue with the high level radioactive waste, but before you have to finally declare the reactor at the end of its life, the amounts of that are small. I'm sure that with proper attention and maintenance, they are pretty safe - the French seem to think so - so what is it about them that scares people ? In these days of hysterical eco-bollox, I would have thought that the advantages, and even disadvantages, far outweighed the (possible) impact of continuing to burn fossil fuels ?

Arfa

This is England, home of the Daily Mail and Fear Of Foreign Plumbing.

It's well known that heat pumps attract foxes and gypsies, who will then steal your antimacassars.

State of the art in this is Dutch greenhouses. They have some interesting systems recently where they store excess heat in the Summer by warming underground water, then extract it in the colder part of the year.

Also any claim that "technology X only works in America because they have plenty of land" looks a bit flimsy if the over-crowded Dutch manage to make it work as well.

tim.... wibbled on Monday 05 July 2010 11:12

No, that's exactly what this chap was saying - they *can* extract practical heat from a few degrees below freezing[1] in test apparatus. They're also trying to use CO2 as the refridgerant which isn't easy but as I understand, makes for a better machine. He didn't say that affordable such machines were available yet, just that there was a good chance there will be.

I think it all comes down to the fundamental anti-science bias of our current society.

You are Russia. Its is the cold war. Reactors make plutonium for bombs. And a little el;electricity.You have an army of agents provoocateurs in every European country, mounting a campaign of propaganda and disinformation. Your natural targets are organisations of people who don't like their government. CND, the communist party etc etc. You spin the facts and where the facts are not clear, you raise spectres of unreasoning panic.

QED

its really that they are just bloody expensive, and require the complete heating system designed to use them.

Give it time.

PV cells themselves might return their invested energy eventually, but add the rest of the system and it doesnt look likely

NT

If you go deep enough, you can use small areas of land.,. The final issue is whether the average summer insolation is more than the winter draw over the same land area.

in general, it is. Cities have to heat more land area proportionately, BUT with high rise buildings in close proximity, heat requrements are a bit less anyway.

AND the summer requirements for aircon means you can charge up heatbanks underground.

Of course, its a big investment, and needs to be done at design stage. You cant really get the best with retrofitting.

Some interesting stuff is going into big office blocks and the like tho.

HOWEVER the actual capital costs of it all are interesting compared to say - simply building 50-100 nuclear power plants. It might be cheaper to simply burn the electricity. Or the uranium as it were.

Oh I think they will return the energy taken to make them all right. Not sure about the energy to transport install and service them.

We the country will construct whatever energy facilities we need. Probably nuclear, if not then other options. I dont think there's much risk of us chosing to go short because of some foolish greenwash. At the end of the day no country chooses economic meltdown, political approval seeking only continues for as long as it doesnt cost too much. Any day we want more energy we can choose to have it, thus there is really no shortage.

NT