Wednesday, June 8, 2011

Solar Power

I've always thought that the government should have introduced a tax on carbon pollution years ago using at least some of the money to fund research into renewable energy sources.

It may be simplistic but the only real solution to climate change is the development of cheap renewable energy sources. The debate really is over how we get there. The simple logic of a tax or emissions trading scheme is to increase the cost of polluting. Increasing the price of polluting encourages polluters to pollute less. This in turn will increase the incentives for companies and entrepreneurs to seek ways to cut energy costs and develop alternatives. Governments need to fund basic renewable energy research. Imagine if the government had used some of the super profits of the mining sector over the past 10 years to fund research into renewables.

I'm pretty sure that subsidising rich people to use existing solar technologies on their rooves (thus raising the cost of electricity for poor people) is not the way to encourage new solar innovations. Rather it is a sure fire way to build resentment about doing something about climate change. In other words it increased the price of electricity without making any substantive difference to dealing with climate change.

One such solar innovation is reviewed by Giles Parkinson in Climate Spectator and sounds very promising indeed.

Supercharging solar

One of the reasons I find solar technology so fascinating is that there is an inexhaustible source of energy and myriad different ideas on how to capture it.
Unlike coal and gas, where the technologies are pretty much standardised – although there is a lot of effort now in improving the efficiency, and thereby lowering the emissions – solar is a new discipline at the commercial scale, and the race is still wide open to find the system that best captures the energy at the least cost.
Most solar thermal technologies have focused on different ways of heating water or other liquids and creating steam to drive turbines – be they in flat mirrored arrays called linear Fresnel, curved mirrors such as parabolic troughs, dish-based technologies that look like space telescopes, or solar towers, where the energy of an array of heliostats (mirrors) is focused on one spot.
A new solar array at the CSIRO’s energy research centre in Newcastle is the world’s largest demonstration of a new technology that uses concentrated solar energy to heat air rather than liquids. In many ways it works the same as a gas turbine: compressed air is heated, and then the air expands through a turbine to create power. “We’ve just eliminated the combustor,” said Robby McNaughton, the engineering manager at the National Solar Energy Center, during a visit to the centre last week.
The technology is known as a solar air turbine, but it’s official name is a Solar Brayton Cycle. And because it needs no water, it is uniquely suited to Australian conditions, where the best solar radiation often coincides with the least amount of available water. And because it lacks the complexity of rival technologies, and can operate as a modular, stand-alone system, it is also suitable for remote locations such as mine sites.
The CSIRO is not yet talking costs per megawatt hour, but it sees its big opportunity in undercutting the price of diesel, which is soaring because of rising fuel and transportation costs. In fact, the rising cost of diesel is proving to be a fillip to a range of renewable technologies in Australia and overseas – wherever there is no coal- or gas-fired energy grid.
“Until you build it it’s very difficult to estimate cost and performance. What you are hoping is that cost of operating this is less than cost of running diesel,” McNaughton says. “This technology is more suited to the smaller scale – I suspect you will see these in the ranges of 1MW-10MW, whereas steam plants will run into the 100s of megawatts.”
The installation at the Newcastle suburb of Mayfield West, built in conjunction with the Australian National University, boasts a 30m tower and more than 440 heliostats, which focus the sun’s energy on a single receiver and can generate temperatures of more than 900°C. Under the current deployment, the field can generate 200kW of electricity or 1MW of thermal energy. Efficiencies are expected to improve dramatically.
The solar field has been commissioned in this past month, and a gas turbine will be installed later this year. “Once we prove that the whole cycle works, then we will start to work out how we can get it hotter,” McNaughton says. The CSIRO has got to 900°C and is aiming for 1500°C. “Beyond this stage it is the industrial partners that take hold.” The CSIRO is hopeful that a commercial partner will take the technology and build a demonstration plant, possibly in the 10MW range.
The new solar array has been erected alongside another array that has also delivered ground-breaking achievements in using solar energy for industrial uses. Known as SolarGas, the technology has been under development for more than a decade, and essentially captures the sun's energy in an endothermic process (chemical reaction caused by absorbing heat), which transforms the natural gas and water feedstock into a higher energy product. The CSIRO says it is a bit like 'solar supercharging' the fuel, and one of the remarkable features of this chemical reaction is that the reformed gas has an energy content around 20-25 per cent higher than what was put in.
McNaughton says there are numerous potential uses, most notably in the industrial sector. (He says areas with the best solar radiation can operate at 95 per cent capacity and be quite predictable, and unlike solar PV, which tends to operate best for just a few hours a day, solar thermal can deliver a much flatter curve over longer hours.)
The most interesting application, however, might be using the system to create “solar fuels” such as diesel and methanol, because the product can be stored, transported and exported in liquid form. It’s a fascinating thought – transport fuels created by the sun – and it happens that a lot of Australia’s best solar radiation can also be found with accompanying gas reserves.
The technology may also be able to be used to create solar hydrogen, suitable for powering fuel cell-powered vehicles, and using a combined cycle gas turbine for electricity generation, the CSIRO says SolarGas can achieve efficiencies of around 60 per cent, much higher than the 40 per cent achieved by conventional Steam Rankine Cycle power generation.
The CSIRO is also pursuing avenues in thermal storage, using different types of salts and fluids and heat transfer systems, and a high temperature steam project, looking to generate higher temperatures from the more “traditional” solar thermal technologies that look to create steam to drive turbines. The hotter the steam, the more efficient, and cost effective, the system becomes.

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