Geoengineering and solar power

 

One of the more drastic approaches to addressing climate change has been the concept of geoengineering, in particular ejecting particles into the upper atmosphere to cool the planet. 

The idea has been based on natural incidents in the past where massive volcanic eruptions have been observed to have a cooling effect. When Mt. Pinatubo erupted in 1991, airborne sulfur reduced temperatures around the Earth for about two years following the event.

While the controversial idea has gained some support with scientists as an absolutely last ditch effort to dampen the impact of climate change, the long term effects remain unknown. However, according to the USA's National Oceanic and Atmospheric Administration (NOAA), such a move would see reduction in electricity generation by solar farms that concentrate the sun's energy using mirrors and lenses.

In such a scenario, for every watt of sunlight the particles would reflect away from the Earth, another three watts of direct sunlight are converted to diffuse sunlight. Flat plate and evacuated tube solar hot water systems and solar arrays based on photovoltaic panels, such as those used on home solar power systems and some solar farms, can utilise diffuse sunlight. However, large solar farms that concentrate sunlight for maximum efficiency depend solely on direct sunlight and cannot use diffuse light.

According to the NOAA, after the eruption of Mt. Pinatubo, peak power output of solar farms in California fell by up to 20 percent, even though the stratospheric particles from the eruption reduced total sunlight that year by less than 3 percent.

As solar power is one of the best hopes for moving away from fossil fuel based power generation, based on the NOAA's findings such a drastic move to curb the effects of global warming could not only have wide ranging unknown negative consequences on the environment generally, but actually see the need for burning fossil fuel in high quantities extended.

Solar Hot Water Most Efficient

 

While an increasing amount of electricity entering the grid is being generated from renewable sources, much of it is wasted on tasks such as heating water that would be best performed by solar hot water systems installed directly on homes. In India, some cities have made it mandatory for new buildings to install solar water heating systems before they can be occupied.
 
According to researchers in India and reported in the International Journal of Global Energy Issues, a solar water heating system has a payback period of just two years. 
 
The researchers from the Dr Panjabrao Deshmukh Agricultural University in Maharashtra, India,  compared solar hot water production per litre with electrical energy approaches and found that solar heating provides 57 percent of the internal rate of return. Their study was based on a  1000-liter system operating at a university hostel.
 
The team estimates that a solar hot water system will effectively pay for itself five times over, given an estimated working life of about twenty years, however the new solar hot water rebate system now in operation in Australia means that Australians may get an even better return on their investment.
 
In Australia, electric and gas hot water systems accounting for approximately 20% of a household's greenhouse gas emissions. By installing a solar water system, householders can significantly reduce these emissions and also save up to 75% of  water heating costs.

The two most common types of collectors used in a solar hot water system are flat plate and evacuated tube. Flat plate collectors contain copper piping running through a glass covered collector, often connected to a water storage tank on the roof. The hot water can then thermo-siphon itself in and out of the tank.
 
Evacuated tube systems use glass vacuum tubes with copper piping running through the centre. The copper pipes are all connected to a common manifold that is in turn connected to a slow flow circulation pump. This pumps water to a storage tank below and the hot water can be used at night or the next day due to the insulation of the tank.

News for Friday 13 March, 2009

 

• Solar Powered Desalination For South Australia
  

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