"you don't actually need to be in a volcanic area to get useful heat from the ground."
No, you don't but economics rules. If it isn't cost competitive with current fossil fuel solutions, it won't happen. The energy used will be the cheapest available, and that's fossil fuel currently. Costs of fossil fuel will have to rise dramatically to make many of the alternatives competitive.
you don't actually need to be in a volcanic area to get useful heat from the ground. They are drilling a whole in the centre of Newcastle-upon-Tyne (UK) for a district heating scheme and that is around 1800m deep. You can also use ground-source heat pumps in your own garden for low grade heat, and if you run that off solar power (for the pumps) you get heating for free.
Solar does have a problematic waste stream. It's mass produced like any other semiconductor using hundreds of toxic and corrosive fluids and gasses, each batch producing upwards of 9 pounds of toxic waste and thousands of gallons of heavily contaminated water (source:http://towardfreedom.com/health/154-toxic-chips-1299)
Environmental friendliness is not the reason the environmentalists are trying to push it onto us, the real reason is because then it creates an artificial scarcity of energy to force us to turn the clock back to the 17th century. Most people support radical environmentalism.....until they discover what the real costs are.
There is a large geothermal plant in California. But, as DMcCunney says, unless you want extremely expensive drilling and maintaining, it is all about location, where the hot springs are already near the surface.
And I bet German's aren't too enthusiastic about Thorium, considering they spent many 100s of millions on a Thorium reactor that ended up getting shut down years ago because it was too expensive to run.
I always get very amused about the energy discussions. There is too much doctrine, advocacy bordering on religion. The math on the various sources with their pros and cons is quite well known. We can even factor in extrapolated trends of existing or possible future technologies in it. And the cold math say that today and at least for the next 20, 30 years we will HAVE TO HAVE substantial nuclear or fossil burning component. It can be argued that the cost calculus of the nuclear underestimates some long term costs and the risk however the same could be sad about the past calculus of the fossil fuel options. Now we do not have any more luxury of naivete: if we keep burning we will be toast. So better it will be nuclear ...
"why don't we ever hear about Geothermal?"
Three words: location, location, and location.
Iceland makes extensive use of geothermal, because they have numerous hot springs. Other places are not so fortunate.
Look into what it would cost to *drill* that 5 mile deep hole, and use the geothermal energy to produce power. The upfront costs would be horrendous, and the payback periods would be extremely lengthy. It simply would not be cost competitive with current alternatives.
Similar comments about location apply to hydro-electric power - pretty much all the places you *can* dam and run the water through turbines to spin generators *have* been, and little growth is possible.
When we talk about energy systems that don't have a problematic waste stream, why don't we ever hear about Geothermal? Granted, there are some technical hurdles to overcome (e.g. drilling a 5 mile deep hole) but no mysteries (like fusion power has).
Junko's comment that her engineer father made a solar installation on the family home in Japan points out that when we talk about solar power, we have to define what we are referring to.
Back in the 70's, I worked for a HUD/ERDA sponsored initiative to promote alternative energy. OPEC was in first flower, gasoline prices were rising over $1/gallon, and there was strong interest in reducing dependence on foreign oil. What we pushed was what Junko's dad apparently did: solar hot water heating. Hot water heating was about 20% of the average residential energy bill, and a solar hot water installation had a relatively short payback period. We were aware of photovoltaics and other alternate energy sources, but they all cost too much to be viable.
The gyrations around China are no surprise. Photovoltaics are semi-conductor electronics, with the same sort of economic fundamentals. A bunch of Chinese vendors saw a market in solar and jumped into the ring. Supply far outstripped demand, prices dropped, and some of the Chinese vendors went belly up.
Solyndra was a source of grim amusement, with the big question being why anyone thought a US based photovoltaics manufacturer could compete with Chinese vendors with far lower costs.
Speaking personally, I see the Chinese presence as helping the overall solar market. The biggest roadblock to alternative energy is cost. The energy used will be the cheapest available. Alternative energy never really took off as proponents hoped because fossil fuel based energy was still cheaper than alternatives.
Cheaper solar panels from China mean lower costs for vendors doing such things, and the possibility of greater sales into a broader market. The Chinese can have the razor thin margin commodity manufacturing business making the underlying solar cells. The value is in other areas of the market, taking those raw materials and making useful products,
Solar without storage has limited capability though and we have not solved the storage issue yet. In many areas, Japan included, winter collection is too low for solar to solve the energy requirements.
Our present Nuclear reactors are unfortunately Uranium based. Expect to see thorium cycle which is significantly safer start to come into the forefront.
Combo SolarPV / SolarThermal panels are readily available though not at the low costs of SolarPV. The low cost currently of natural gas has created less incentive for SolarPV.
In terms of waste heat in your attic being used to cool your house, thermodynamics tends to work against you, i.e. the difficulty of extracting energy with small temperature differentials. Total energy stored in heat in your attic is not really large either.
"Heat" from the sun is really just longer wavelength radiation and concentrated PV does collect longer wavelengths to some degree.
Solar Thermal systems are readily available and used for not only solar water heating, but in southern climates is used to drive air conditioning.