Global Warming Solutions
The generation of electricity from fossil fuels in power stations is generally only about 40% efficient. The internal combustion engine has an efficiency of only 20-25%. Conversion of solar energy into electricity is less than 20% efficient. Despite the brilliance of so many of our technological achievements and despite the imminence and severity of the problems of global warming, it remains the case that the conversion of heat into mechanical or electrical energy is notoriously inefficient. This paper describes a new approach that may offer much higher conversion efficiencies.
Hot gases rise. The combustion of fossil fuels in a power station produces a continuous stream of hot gaseous products that rise. The upward flow of the products of combustion could itself directly drive a turbine to produce electricity. The residual energy of the flue gases can then be used to preheat the incoming air for combustion. Indeed generation would be most efficient if the preheated incoming air was used to drive a turbine. By rigorously eliminating all possible energy losses it should be possible to generate electricity with over 80% efficiency.
The principles described should also apply to motor vehicle engines. Illustrative examples have been devised of possible design. Continuous combustion of fuel produces a stream of hot rising gases whose energy can be converted into rotation which is conveyed to the axle. Again if the products of combustion are used to preheat incoming air, energy losses are minimised and a conversion efficiency of heat into mechanical energy of over 80% should be possible.
Solar energy falling on panels produces warm air which rises. The flow of warm air can be used to drive a generator. If the residual energy of the warm air is used to preheat incoming air and all energy losses minimised, conversion of incident solar energy into electricity with over 80% efficiency should be possible. This is the Holy Grail. The materials and technologies described are cheap and relatively low tech. If it is possible to convert solar energy into electricity efficiently and cheaply that is the energy problem solved and global warming solved. Hence the title ‘Global Warming Solutions’.
Natural gas is now the leading fuel for electricity generation in Britain giving modern power stations very high controllability. If only a stoichiometric quantity of air is used the combustion gases will have a temperature of 2000° C. The combustion chamber should be designed to allow a large excess of air so that the rising flue gases are at below 500° C.
A magnet could be designed of suitable geometry and with buoyant light materials surround so that it rotates efficiently and ‘weightless’ under the upthrust of the rising incoming gas flow. There are no major energy losses in the above configuration. The heat content of the combustion gases is transferred to the incoming air that rotates the magnet and generates electricity. Any residual heat is absorbed in the water exchanger. An overall efficiency of over 90% should be possible.
In the cross-section above the central rotating arms will be linked to an axle to convey rotational energy to the wheels. As the fuel burns, combustion gases rise inducing rotation of the asymmetrical arms in an anti clockwise direction. Fresh air is drawn in from the bottom – it will be pre-heated by the asymmetrical arms as it enters the combustion chamber.
There could be several layers (3 to 20) of such rotational arms to allow effective energy transfer from the rising hot gases to the rotating mechanism and from the latter to pre-heat the incoming air. If there is an abundant air supply, the central temperature could be below 500° C but will fall as we pass to outer layers ideally at 100° C. If such a design were achievable it would mean a rotary engine of over 80% efficiency.
Dimensions above for the generation unit could be one metre diameter and the heat exchanger 5 metres height. The solar absorption surface could be 100 metres x 100 metres with the sloping glass one metre high at the perimeter and 5 metres high at the centre. The mouth of the warm air exit pipe would need to be 1-5 metres above the cold air entry level to drive the system.
The geometry of the solar generator as drawn may appear inconvenient but it could be sited on a South facing hillside with the generator at the highest point. The only major energy loss above is through the glass of the solar collector – certainly double glazing or perhaps triple glazing with glass of low thermal conductivity will be needed to reduce such energy loss. For the absorption of solar energy the Solar One Power Plant in California has achieved an efficiency of 96% absorption using a special type of paint. The Wells turbine can capture as much as 90% of the energy of air flow. If heat losses through the glass can be minimised conversion of solar energy into electricity with over 80% efficiency should be possible.
Solar electricity is considered wildly uneconomic in the UK – but even in Britain, in Aberporth solar energy influx is 600 kWh/sq metre/year. At a value of 2 pence/kWh, an area of solar absorbers of 100 metres x 100 metres with 80% conversion efficiency into electricity would provide annually about £100,000 electricity per hectare of land. The capital cost of the equipment described would be repaid in a year. In California, most of Southern Europe and large areas of the developing world solar influx is 3-4 times as great.
If solar energy could be converted into electricity efficiently and cheaply that solves the energy problem and global warming. There is however a seasonal mismatch, a day/night mismatch and a geographical supply/demand mismatch. The advanced countries have highest energy demand whilst the potential for solar energy is greatest between the tropics. The best solution is to use solar electricity to generate hydrogen. This could become the fuel for transport using the fuel cell, for industrial and home heating as natural gas supplies diminish and of course could regenerate electricity. A new world trade could develop in the supply of hydrogen.