SOLAR CHIMNEYS A Promising Alternative By Salah El-Din E. El-Metwally Wai-Fah Chen David Ma University of Hawaii at Manoa 1
Contents Solar Energy Technology with emphasis on Solar Chimney How much desert needed to meet energy demand? Cost and Economy estimates Pilot Project Previous research 2
SOLAR ENERGY UTILIZATION Five technologies utilize the sun's heat to generate energy: Photovoltaic technology Metal Membrane Concentrator Systems Distributed Collector System with Trough Concentrators Central Receiver Systems - Solar Tower Plants Solar Chimneys 3
Dish Stirling Systems A large hollow reflector is suspended in such a way that it can track the sun. The reflector has an energy converter to convert the concentrated solar heat into electricity. 4
Distributed Collector System with Trough Concentrators These troughs are suspended in such a way that they track the sun however around one axis only. 5
Central Receiver Systems - Solar Tower Plants The central receiver is placed on a tower, between 50 and 150 meters above ground. 6
Solar Chimneys o In the solar chimney, three well known physical principles; the greenhouse effect, the chimney and the wind turbine are combined in a novel way. 7
o o o Incident solar radiation heats the air under a large collector roof. The temperature difference causes a pressure drop over the height of the chimney resulting in an upwind. The upwind is converted into mechanical energy by a turbine and then into electricity. 8
Experimental Solar Chimney Chimney height Chimney radius Mean collector radius Mean roof height Wind turbine diameter Wind turbine speed Temperature increase Collector efficiency Turbine efficiency Frictionless factor Upwind velocity under load Upwind velocity on release Nominal power output 194.6 m 5.08 m 122.0 m 1.85 m 10.0 m 1000 rpm 20 C 32% 83% 0.90 9 m/sec. 15 m/sec. 50 kw Experimental Solar Chimney in Manzanares Spain. Sponsored by the Ministry of Research and Technology, Federal Republic of Germany. 9
Annual energy production as function of chimney height and collector diameter for 2300 kwh/y global radiation. 10
Dimensions of power plants and energy production for 2300 kwh/y global radiation 11
Chimneys' electricity generating costs in relation to mean installed power 12
Specific installation costs and their distribution in relation to mean annual electricity output 13
Advantages of Solar Chimneys: 1-3 It makes use of global solar radiation, including diffuse radiation when the sky is partially or completely overcast while other solar technologies not. Their natural thermal storage capacity, which has reduced costs and guarantees operation at a constant rate until well into the hours of darkness (and throughout the night with largescale installations). 14
Advantages of Solar Chimneys: 2-3 Aside from the turbine and generator there are no moving parts or parts that require intensive maintenance; No water is required to cool mechanical parts as in fossil and nuclear power plants or even in other solar thermal power plants such as the distributed collector system and the central receiver system, which need a complete cooling system with a large consumption of sweet water which is very scarce in sunny countries. 15
Advantages of Solar Chimneys: 3-3 It features a simple, low-cost design utilizing know-how and materials that are also available in Third World countries (glass, concrete and steel) A high proportion of the costs is accounted for by work that is simple and can therefore also be done by local labour in developing countries, which would benefit the local labour market while at the same time helping to keep the overall costs down. 16
Electricity production costs of relevant renewable energy technologies 17
Energy Storage For 24 hours continuous flow of electricity with almost constant rate. Storage is achieved by increasing the size of the collector and placing sealed water bags at the ground of the collector to absorb a part of the lost energy and later on this energy is reflected thus heating the air. Storage may increase the cost of the plant 50%; however, it results in an additional 100% of electricity output. 18
How Much Desert Needed for Meeting Energy Demand?1-3 Based on: 1. 200MW Plant with Storage 2. 2500 kwh/ y Global Solar Radiation Land The 200MW power plant with storage produces annual energy 1400GWh and consumes a land of diameter 4000m. This means that 1.0square meter produces 111.5kWh. 19
How Much Desert Needed for Meeting Energy Demand?2-3 If we account for access roads and other facilities, conservatively we can say that 1.0 square meter produces 100 kwh. If Car runs 15000 km/year requires 1500 litre of petrol or 18000kWh. This car requires a land of an area = 18000/100 = 180 square meter. An individual in Western Europe consumes on average 4kWa/a; 50% of this energy is consumed for the car. 20
How Much Desert Needed for Meeting Energy Demand?3-3 An individual in Western Europe requires a land of an area 350 square meter for his energy demand. A 200MW power plant will cover the energy demand of 40 thousands inhabitants in Western Europe. 21
Cost and Economy Estimates (Based on Prices of Year 2002) Energy cost (kwh-$) referred to Tushka solar radiation Option Life span* Interest Rate Inflation Rate Without storage 100 MW 200 MW With storage Without storage With storage (1) 20 8% 3.5% 0.071 0.053 0.059 0.044 (2) 20 4% 3.5% 0.053 0.040 0.044 0.033 (3) 40 8% 3.5% 0.063 0.047 0.052 0.039 (4) 40 4% 3.5% 0.042 0.032 0.035 0.026 * of collector and mechanical parts assuming that the chimney will last 80 yr 22
CONCLUSIONS Solar energy utilization is the only answer to the greatest threats in the history of mankind. It is both technically feasible and affordable; a fraction of the earth's desert areas to obtain from sufficient solar energy needed to avert these catastrophes. Solar chimney seems to be the most promising system for large scale consumption. 23
Thank You 24