Using miners as heaters is pretty insightful. Sadly it can't work in real life. At 60 centigrade internal temperature the GPUs fry, and waste heat from coiling them is probably 40-45 degrees at most. That's not really very useful for heating, maybe only if you blow the heated air directly into the rooms. Electric heating is also very expensive, and is often employed in a heat pump configuration that uses electricity to drive a motor (mechanical work), and achieves much better efficiency than simple Joule heating. It's also not needed year-round.
I was thinking of ASICs that have a large footprint and a huge heat sink attached to them (i.e. the size of a domestic radiator). Even if they were only 50% as efficient as central heating then the school/hospital would pay < 50% of the electrical costs and you'd have a huge competitive advantage.
I can't see how a heat sunk ASIC could be anything other than near 100% efficient. Where does the energy go if it's not heat? light? sound? potential? chemical potential? Information transmission? Information entropy!! Wow. That'd be something. My guess is that you could convert at least 95% of all that electrical energy into heat. Where else would it go?
While we fixate on electricity as the main waste for Bitcoin, in reality the capital costs of designing and manufacturing rigs will be quite high. Allot of resources will go into manufacturing, with the associated environment impact. Electronics manufacture requires rare, pure, toxic substances, precision industrial machinery, world wide shipping etc. If Moore's law holds for mining bitcoins, the old hardware might be tossed before it has a chance to equal the environmental footprint of it's production. This is certainly the case with consumer electronics.
You'd create a spread out 1000-core ASIC hashing wafer. 1m^2 x 1m^2 might do it. You're hashing rate is your temperature control and if you cranked it right up then the fusebox would melt. Your only limit is the amount of money you want to spend on electricity and the fuse current limit from your electricity supplier.
So let's assume you can make an electric hashing heater that's not too noisy and doesn't produce light - although that might be nice too - say 95% conversion to useful output. The question then is the relative price of energy sources.
Natural Gas - 4.1p / kWh
Electricity - 13p / kWh
* source
http://www.biomassenergycentre.org.uk/portal/page?_pageid=75,59188&_dad=portal** These are bulk fuel purchase prices.
Looking at
http://www.decc.gov.ukIt would appear that domestic costs for England 2010 for typical amount of use is...
Gas - 3.5p / kWh
Electric - 10.4p / kWh
Assuming 98% efficiency of a condensing gas boiler or 70 -80% for conventional boiler. You could expect an all electric heater to cost about 3 times more than the equivalent gas boiler heater. Once you factor in the additional costs of manufacture etc then you're looking at getting less than 10% of the bill covered. When you also take into the account that these people might have environmental concerns about the tripling of their fuel bill (even though they'd only be paying a third and energy consumption was ~ the same but when's logic ever mattered to an environ-mentalist, right?) then it's starting to look like a non-starter.
I've convinced myself that this isn't workable
but, the point is that their is a competitive advantage to measuring 'real' energy use by hash computation.
Bitcoin air conditioner anybody? I guess that's not possible either or you'd have servers farms that self-cool.
I'm still of the opinion that Bitcoin needs to measure real world 'proof-of-work' or it just won't succeed due to the huge demand in energy to run the thing.
If only there was some way to convert the hashing heat back into something more useful...
Quick! Someone invent a turbine that hashes as it spins!
Hmm... interesting stuff this Bitcoin. Makes you rethink all sorts of things.