The basic concern is that much of the energy we use ends up as heat, even as in heating the circuits of your computer or your fancy phone. Some turns into light or radio waves which are absorbed as heat by surfaces.

If we use nuclear power, for example, we are making heat out of uranium.

Currently humans use 16 terawatts (TW) of power at any moment, compared to 120,000 TW of solar power absorbed by the Earth at any given time. Energy consumption has been rising by about 2% pa for the last century. Chaisson’s original article based his calculations of (only) 9 billion people by 2100. Those in the OECD will increase their energy usage by 1% pa. The rest will increase theirs by 5% pa until parity is reached, and 1% pa from there. On this basis even if GHG emissions cease immediately the world will warm by 3C in 320 years, when he has us using 4800 TW. Given that we have already warmed by 0.8C since pre-industrial times and a further 0.5C or so is estimated to be in the pipeline, there’s little margin left even if you foolishly think we can warm by 2C with impunity.

There are other sources of power that won’t contribute to global warming. One is hydro power. A second, as John D pointed out on the previous thread, is tidal power, because the gravitational pull of the moon is there and is not going away. A third is bioenergy, which has other problems in some of its forms.

By the way, Chaisson calculates that the modern American uses 12.5 kilowatts of energy, whereas your average hunter gatherer used only 0.15.

There is other interesting material in the article about the effects of wind and solar on the climate. In California, for example, temperatures behind the wind towers were found to be higher at night and as much as 4C lower by day. We only produced 0.2TW from wind worldwide in 2011, so it is thought that we can go much further without affecting the weather generally but the ultimate limits of extractable energy from wind are much lower than solar. At most there is 68TW available, but one estimate indicates only 18TW may be extractable.

Huggy suggested a global grid of ultre-high voltage direct current (HVDC) transmission lines. Perhaps we could do one along each of the Tropic of Cancer and the Tropic of Capricorn, with lateral connections through the America’s, Europe/Africa and Asia/Australia.

Grossmann et al have been working on the concept of large solar regions connected by HVDC, for example here and here.

Here are a few more matters to consider.

In November last year Giles Parkinson at Climate Spectator spoke to former Ausra chief David Mills about a study Mills had done with former Ausra R&D specialist Wei Li Cheng and US Department of Energy analyst Phil Larochelle looking at whether solar and wind could supply enough electricity to run the US economy, including transport, using hourly data from 2006 and existing technology. They found that they could. Their concept assumed a HVDC network that replaced flatlining baseload power with “a system of flexible and inflexible energy mechanisms based around wind and solar and other sources.”

China, we are told, is installing more HVDC lines than any other country in the world.

You will be aware that there has been a lot of discussion about the prospect of a grid parity cross-over with solar. Back in June last year we looked at whether solar had come of age.

Parkinson’s update after Mills’ talk at the Solar 2011 conference last year made this comment on cost:

“People say we need baseload plans, but we don’t,” he says. Instead, grids can work perfectly well with a mixture of inflexible supply (wind that blows whenever it wants), and flexible supply (solar thermal with storage). Mills has yet to release the financial modelling for his scenario, but notes that wind is already cheaper than new-built coal in the US, and solar thermal with storage, and used as a peaking plant, will be competitive with peaking gas.

Mills was calculating only on large scale concentrated solar, which was his business, rather than on PV, whether in local distributed energy situations or larger arrays, as in this image from Germany:

German PV solar array

Also from the article:

The UNSW study, based on simulations of Australia’s energy needs in 2010, found that the entire supply could be met by a mix of solar thermal with storage, wind, solar PV, existing hydro and peaking gas plants running on biofuels. Only six hours of the year fail to meet the NEM’s reliability standard, all in evening peaks in the winter months.

That study involved Mark Diesendorf, and I worry about him.

A few weeks later Parkinson was at it again, suggesting that solar could be essentially free. If you include the cost a solar array in your mortgage and use the savings in electricity costs to pay off the mortgage you can pay off the mortgage early.

The International Energy Association (IEA) pointed out last year that in 90 minutes, enough sunlight strikes the earth to provide the entire planet’s energy needs for a year. They tested the limit of what they thought could be achieved with solar after 2035 if for whatever reason the world decided to move away from nuclear and carbon sequestration and storage (CCS) technology. I’ve taken a brief look at their vision in a separate post along with the notion of distributed generation. The ultimate would be to combine local generation and sharing with a word-wide network.

Clearly there is much for policy makers to think about and questions can be asked about Chaisson’s scenario. The IEA, for example, sees the world in 2060 as one that is four times richer, but through energy efficiency measures using only 50% more power.

Meanwhile Australia’s outlook for solar was characterised yesterday as not so sunny as we stumble towards establishing large-scale solar projects. The Clean Energy Council said a number of other countries have solar markets that are more mature than ours.

One is India, which is now generating cheap solar (8.78 rupees per kilowatt-hour compared with 17 rupees for diesel) in pursuing its “Solar Mission” to install 20,000 megawatts of solar power by 2022.

Based on AEMO market data, you can see how much power south-eastern Australia’s wind farms are actually producing, and compare the patterns to total demand.

For what it’s worth, July 2010′s performance is particularly illustrative in my view.

Hat tip Barry Brook.