Electricity
From Envirowiki
Electricity is the flow of electrons from one place to another, usually converting electrical potential energy into another form of useful energy. It can be used for many applications, from kinetic energy (movement), lighting, heating, to telecomunications.
Electricity production, most often from fossil fuels, is one of the largest contributors to global warming and climate change.
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[edit] 1 Electricity Generation
There are three important issues that must be considered when looking at electricity generation. These are:
- The CO2 per kWh generated
- Cost per kWh generated
- Whether the source can be considered as base-load or a contribution to a larger base-load system.
[edit] 1.1 CO2 per kWh generated
This is an important point which is frequently oversimplified. For example it is said that Hydro or Solar power has no CO2 contribution. Whilst the contribution can be small, it is not always insignificant. Building of hydro power stations uses a lot of concrete which produces CO2[1] and the effect on the flooded land and decaying vegetable matter must also be factored in. In the case of Solar, considerable energy is used in the construction and installation of the panels. The payback time in CO2 terms is somewhere between 1.5 and 3.5 years. With Nuclear power, there is some debate as to whether the impact is ever repaid[2], whilst at the other end of the spectrum, the nuclear lobby argues that nuclear power is almost CO2 free. Certainly in accounting for CO2 emissions, the latter is assumed. The result is the countries like Japan, France, the US and UK are rated as having relatively low average CO2/kWh because of nuclear power.
[edit] 1.2 Financial Cost per kWh generated
It is often said that "power from the sun is free". Sadly this is not the case. Solar installations of all kinds are expensive and if installed in areas where there is moderate sun may have a financial payback period as long as 60 years (ie. practically never, due to life cycle constraints), although this is rapidly improving. Of course the sunnier the location of the installation, the shorter the payback period. In many European countries the feed in tariff (the price the utility will pay you for electricity you sell them) is much higher than the price you pay. This dramatically reduces the payback period. For example Germany has a feed in tariff of 50 cents/kWh to as much as $1/kWh[3], reducing the payback time to about 12 - 15 years.
Electricity can be generated from solar thermal power by using concentrating mirrors to produce energy using steam to drive turbines, a Stirling engine to drive a generator[4], or stripping ammonia into hydrogen and nitrogen for later use as a heat generator[5][6]. These options may be cheaper than flat panel solar photovoltaic systems but it is interesting to note that in Victoria, Australia, a 154 MW system is being built using concentrating mirrors focussed on photovoltaic cells. Obviously the jury is still out about the cheapest way to generate electricity from solar on a large scale.
Another question to ask is why governments are heavily subsidizing rooftop domestic solar when this is probably the most inefficient[reference needed] method? It has a minor advantage that the energy is distributed and used at the source. However given that the grid exists already and is large enough to cope with the demand, it doesn't appear to make sense. True the population is footing some of the bill for domestic systems but the economy of scale of large installations more than makes up for that. Contributions to answer this question would be welcome.
Decentralisation of power generation, especially microclimate-dependant systems such as solar and wind power, has a number of advantages when combined in a large network (ie. existing electricity grids). Firstly, peaks and troughs are ironed out, meaning that the entire system can more adequately cope with baseload (in a lowest common denominator way). Such a system also means that in the event of a disaster (nuclear meltdown, earthquake, bush fire, etc.), it is less likely that a major percentage of power production could be taken down at once, or even if it is, then SOME power would still be available for vital services. Lastly, contrary to governments' usual plans, a decentralised network would put direct control of power generation into the hands of the people who use it, giving them more of a sense of empowerment, as well as being a source of knowledge about the basic facts surrounding energy generation, of which many people are unaware.
[edit] 1.3 Base-load power
If we are to become anything close to carbon neutral, we will need a significant level of base-load power and/or we will need to significantly reduce our usage of base load power, through energy use patterns, or energy storage. Power from the wind, sun, tides etc. currently does not match the customer demand. Renewable power from these sources needs energy storage and that will add considerably to the cost and complexity of electricity generation as we get to greater levels of power from these sources. Energy storage does exist[7] and is at present being developed by the CSIRO but it is not of sufficient capacity to deal with the problem. The biggest, cheapest and most straightforward method is hydro power, where renewable energy can be used to pump the water back up the hill (see: Gravity battery). However in places like Australia, the relatively small capacity of hydro power would be insufficient. Building more dams has also become problematic, for environmental reasons (however, off-stream dams in already degraded land could also be used, minimising ecological impact). So we must look towards ways of generating large amounts of power which can be supplied on demand.
What are our best options for renewable energy? The main alternatives as we know them today are shown in the graph below. In the cases where there are greenhouse gas emissions, the cost of CO2 has been added at $60/tonne[reference needed], to give a total effective cost.
A graph such as this is of course highly controversial and various camps will claim much higher or lower costs depending on their particular bent.
It is interesting to note that in the media, Nuclear, Solar, Wind and Geo-sequestration are frequently mentioned. How often is Geothermal mentioned in the press? Hardly ever. Why is this so? Maybe it is that both the coal and the uranium industries have powerful political lobbies associated with them. Geothermal obviously doesn’t carry any political clout.
[edit] 2 Hot Fractured Rock Geothermal
Unknown to much of the population, Australia has huge reserves of hot rock geothermal energy. This differs from “conventional” geothermal energy which is associated with volcanic activity and used in New Zealand. In Hot Fractured Rock, (HFR) water is pumped down an injection well into heat-producing granites located 3 kilometres or more below the surface. Temperatures of up to 300 degrees are obtained and the water is circulated through a heat exchanger. Australia’s recoverable HFR resources are capable of satisfying current electricity consumption for over 450 years. The Cooper Basin in South Australia alone could provide emission-free base-load electricity for 70 years. Although it is technologically difficult, it is composed of solvable problems, mostly using existing oil drilling technology. When compared with nuclear with its multiple thorny issues of safe disposal, security against terrorism and accidents, it seems a very attractive proposition. The major advantage Geothermal has over wind and solar is that it suitable for base-load supply. It can be regulated to match the load, rather than being at the whim of the elements.
A major advantage of the Cooper Basin is that it is a long way from any population centres (a disadvantage with AC transmission losses). The Swiss city of Basel has a HDR (Hot Dry Rock) geothermal power station pilot project which has just recently been put on hold, after three earth tremors over three on the Richter scale were experienced. Since then an argument has developed as to whether the drilling allowed minor slippage to occur (a practice used on the San Andreas Fault), thus averting a bigger earthquake, or if it is the cause of quakes which would otherwise never happen.
