Solar Power. Technical Aspects and Environmental Impacts. 6 th March 2011 Sustainable Energy Options (UAU212F) - University of Iceland

Transcription

1 Solar Power Technical Aspects and Environmental Impacts 1

2 Solar Power 1. Introduction 2. Passive Solar Energy utilization 3. Solar Thermal Heat Utilization 4. Solar thermal power plants 5. Photovoltaic 6. Conclusion 2

3 Introduction Using the horizontal collectors magnitudes of 750 to 850 kwh/m²a can be reached in Iceland, according to PVGIS. Iceland is located in a region where the cloud coverage amount is around 70 to 80%, quite high in comparison to places like south Europe where solar power is used in big scale projects. The average temperatures in populated regions in Iceland are around 0 to 8 C 3

4 Introduction 4

5 Introduction Solar energy has the benefits of being a very clean energy source, solar energy systems are noise free and do not release any chemicals into the environment during normal operation. The radiation of energy by the Sun can be utilized in different ways; Solar energy can be used passive The radiation energy can be converted into heat by solar heating systems The process of converting radiation into heat is used in big scale projects like solar thermal power plants Photovoltaic power generation gives the possibility to convert radiation directly into electricity. 5

6 Passive Solar Energy Utilization 6

7 Passive Solar Energy utilization Principle : 1. Building envelop = absorber for the incoming radiation 2. Building structure = heat storage system 7

8 Passive Solar Energy utilization Physical basics: 1. Radiation is reflected, absorbed and transmitted 2. Conduction based on Fourier's law 8

9 Passive Solar Energy utilization Designs: 1. Solar walls where radiation is converted into heat and conducted to the interior of the house 2. Transparent thermal insulations 9

10 Passive Solar Energy utilization Designs: 3. Passive Houses - Building envelope is air sealed and a ventilation system with heat recovery is used 10

11 Passive Solar Energy utilization Environmental Impact CO 2 emissions can be decreased in many countries Possible to calculate optimum thickness of insulation for different cities Amount of fuel consumed and emission to the environment can be reduced by about 30%. 11

12 Passive Solar Energy utilization Situation in Iceland: Building structures are often missing good insulation and ventilation People often are heating and ventilating with the help of an opened window at the same time Good approach Passive houses -> Any house can be upgraded Icelandic winters are mild and summer temperatures quite low -> low energy losses (e.g. Ti - Material) 12

13 Solar Thermal Heat Utilization 13

14 Solar Thermal Heat Utilization Principle : Based on solar systems converting radiation into heat (active systems e.g. Solar collectors) Heat produced within the material is released by heat conduction to an heat medium or by emission and convection back to the atmosphere 14

15 Solar Thermal Heat Utilization Physical basics: Kirchhoff's law - Absorption capability directly connected to emission ability Increase efficiency of solar collectors -> suitable "selective" coatings Efficiency of the collector is the highest if the temperature difference between absorber and the environment is smallest and maximum radiation is hitting the collector. Useful energy for Central European conditions ~ 25% 15

16 Solar Thermal Heat Utilization 16

17 Solar Thermal Heat Utilization Absorber: High absorption capacity within the luminous spectrum and low absorption and therefore low emission capacity in the thermal radiation wave spectrum Mainly copper and aluminum are used, the cover is mostly out of glass For the installation it is important to check the static of the building 17

18 Solar Thermal Heat Utilization High cloud coverage Incoming radiation < 100 W/m² (a flat-plate liquid-type collector) 18

19 Solar Thermal Heat Utilization 19

20 Solar Thermal Heat Utilization Environmental Impacts: If they are installed on rooftops they usually look very much like regular roofs, can have a minor visual impact If collectors are installed in open areas, they impact the micro climate because of the shadow area underneath the solar systems. The solar thermal systems require cooling liquid, which may need change every 2-3 years. Because of the high temperatures that the solar thermal system can reach, it could cause a fire hazard if the coolant liquid were to leak 20

21 Solar Thermal Heat Utilization Situation in Iceland Low efficiency due to low radiation and high cloud coverage (not all time operating) Maybe used in rural areas where no access to geothermal heat is possible Solar collectors have to be compared to heat pumps using geothermal heat probes. 21

22 Solar Thermal Power Plants 22

23 Solar Thermal Power Plants Principle : 23

24 Solar Thermal Power Plant Environmental Impacts: They are generally very large, and need extensive land area. They can have a high central tower which causes visual impact on the scenery. Noise pollution is minimal 24

25 Solar Thermal Power Plants Situation in Iceland: Techniques used need at least an average annual global radiation of kwh/m² to work feasible Annual global radiation in Iceland is around 800 to 1000 kwh/m² 25

26 Photovoltaic 26

27 Photovoltaic Principle : The photovoltaic process is the direct conversion of solar radiation into electricity 27

28 Photovoltaic Physical basics: 1. Photo effect : Photons energy is converted into potential and kinetic energy of electrons 2. Free electrons are leading to an increase in conductivity 3. Doping : electrical potential is created (phosphorus/boron ) 28

29 Photovoltaic Physical basics: 1. Current increase is proportional and almost linear to solar irradiance 2. Increases in temperature leads to efficiency reduction (0,5%/K) 29

30 Photovoltaic 30

31 Photovoltaic Designs: 1. Solar panel market is mainly dominated by PV modules based on crystalline silicon (c-si) cells 2. Thin-film modules presently account for less than 10% of the market 31

32 Photovoltaic Environmental Impacts: To produce photovoltaic solar cells, rare minerals are used During operation PV panel do not emit any gaseous chemicals. But the production still emits some amount of greenhouse gases, in small quantities. During the operation of roof-mounted photovoltaic solar cell, no noise is created and no substances are released. They are also similar to roofs and do not cause much visual impacts. Ground mounted photovoltaic solar cells do need ground space, which might otherwise be used for other purposes. 32

33 Photovoltaic Situation in Iceland: kwh (PVGIS) generated by 1kW peak system (~10m²) with a performance ratio of 0,75 kwh/kw peak Nesjavellir has a capacity of 120 MW -> same amount of capacity an area of ~ 17 km² Not feasible for big scale projects, useful if small energy amounts are needed but no electrical grid exists 33

34 Conclusion 34

35 Conclusion Passive utilization (e.g. passive houses, special insulation) can help to decrease the needed heating demand and can lead to a better living environment Use of solar power plants is not feasible Smaller heat collector units can be used seasonal still having a low efficiency Photovoltaic can be used for electricity production but is senseless for big scale projects 35

36 Conclusion Big scale active solar systems are not feasible compared to the existing systems like geothermal or hydropower systems. They can be used for rural areas where no other form of energy systems are available If they would be used in a small scale the environmental impact would be minimal, possible some visual impact but that could be minimized with good design. 36

37 Thanks For Your Attention 37