Category Archives: Teija Mortvedt

Concentrating Solar Power and Thermal Energy Storage: Possibilities

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As the solar energy movement progresses the efficiency and cost-benefit ratios can be examined to determine which technologies will serve us best. Concentrating solar power (CSP) is one such vein in the solar technology movement. Unlike photovoltaic generation, which converts light energy to electricity, CSP uses thermal energy to produce electricity (Shioshanasi and Denholm 2009). CSP value was analyzed at various sites in the American Southwest. It was shown that CSP is made more valuable by implementing thermal energy storage (TES) which allows for increased capacity of plants as well as greater profit by shifting production to hours of higher energy prices. Despite these advantages, it was determined that CSP with TES cannot be justified at current capitol costs, but CSP alone will become more economic with further cost reductions. — Teija Mortvedt 
Sioshansi, R., Denholm, P., 2010. The Value of Concentrating Solar Power and Thermal Energy Storage. iwse.osu.edu.

 Shioshansi and Denholm worked to model the capabilities and costs of CSP using data from four sites in the southwest: Gila Bend (Arizona),  Daggett (California), Southern New Mexico, and Western Texas. They evaluated plants both with and without TES. With TES a larger solar field could be built and plant layout and size would be dramatically affected. Field size determines plant capacity so this is an important consideration. If the solar field is too small, the power block will be underused and inefficient, 2nd capacity will be lower. If the solar field is too large thermal energy will be wasted because the plant will not be able to utilize all the energy collected.
The study analyzed operating profits of CSP plants with different sized solar fields and three different levels of TES. TES always increased operating cost and it was seen that cost varied significantly with location and plant size. Location differences can be attributed mainly to energy price differences by location.
CSP makes it possible to hold electricity at any moment in anticipation of energy prices the next day.  They assume prices are known only one day in advance although predictions of multiple days may be available in the future.  This feature allows given amount of energy generation to be sold at the highest price but the analysis was based on the assumption of perfect foresight into the future, which in practice is not true. Regardless, it was determined that this model was profitable without 100% foresight.
CSP with TES is currently not an economic option anywhere but in Texas where energy prices, and therefore profits, are higher. It is assumed that CSP is eligible for investment tax credit (ITC) of 30% currently or a possible reduced 10% in the future due to CSP cost reductions. The 30% ITC makes CSP without TES an economic option only at the Texas site, and with TES economic in Texas and Daggett.  CSP will become a more economic with technological increases and cost reductions in the future. 

Implementation of Solar Home Systems in Bangladesh: Feasibility

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In Bangladesh the climate, despite the monsoons, seems well suited for solar energy as a form of renewable energy.  The form of photovoltaics most attractive to the people of Bangladesh is the solar home system (SHS) which would provide electricity for lighting and other uses to households across the country. Currently the people of Bangladesh burn kerosene for lighting and use dry cell batteries mostly for radio.  SHS would eliminate the burning of kerosene and the waste of batteries. It was determined that it would be financially smart for small business and household lighting and entertainment (but not lighting only). — Teija Mortvedt 
 
Mondal, A. H., 2009. Economic Viability of Solar Systems: Case Study of Bangladesh. Renewable Energy 35, 1125–1129.

 Alam Hossian Mondal of the Center for Development Research the University of Bonn studied three villages, Niz Mawna, Barabo and Dhonua to determine whether it was economically beneficial to use SHS’s to provide electricity in order to prevent the use of other non-renewable energy sources.
SHS eliminates the need for kerosene burning lamps, which in turn eliminates large quantities of CO2 emissions. After considering per ton CO2 reduction costs it was determined SHS would yield an annual saving of 70 Taka (60 Taka = 1 USD) per household.
A typical SHS includes a photovoltaic (PV) array, and a rechargeable battery for energy storage.  This system could be implemented via standard solar application on rooftops. These roofs belong to rural customers who are not in the habit of buying large systems, and usually do not buy everything unless they see the perceived benefits of the purchase.  Therefore if SHS is to be implemented it must be seen as a worthy investment by the rural home and business-owners.
It was shown that due to the high initial capital and installation costs, SHS would not be affordable unless subsidized to at least some degree. Once subsidized properly, people would be inclined to purchase the system, resulting in a chain reaction and increased SHS popularity.  However the SHS is only economical for households if they are using the electricity for some uses other than lighting. It would almost always be good for small businesses to utilize, decreasing costs in the long run and decreasing CO2 emissions from halted use of kerosene. 

What a Looker: Solar Power Plants

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Solar energy is a good option for areas of high solar irradiation because it can produce large amounts of electricity at low levels of pollution. One of the only direct pollutants is visual alteration of the landscape where panels are placed. Following EU regulations, Environmental Impact Assessment (EIA) requires a visual impact analysis for large solar power plant constructions. Torres–Sibille et al. (2009) devised a system to judge the aesthetic impact of a given solar power plant.  When compared with real subjective human evaluation indicator used in this study generally explains user preferences well and will be useful in determining where to build solar plants and how best to do so to minimize visual impacts.— Teija Mortvedt 
Torres–Sibille, A. C., Cloquell–Ballester, Viceente–A., Cloquell–Ballester, Victor-A., Ramirez, M. A. A., 2009. Aesthetic Impact Assessment of Solar Power Plants: An Objective and a Subjective Approach. Renewable and Sustainable Energy Reviews 13, 986–999. 

 Torres–Sibille and colleagues at Valencia University of Technology devised their method of aesthetic impact analysis based on expert methodology used to analyze wind power.  Solar power is similar to wind in that it dramatically transforms the appearance of a landscape with out dramatically altering the land itself.  The effect of solar panels is at a much lower altitude than wind power but still obvious.

The researchers focused on aesthetic impact based on visibility, color, fractality and concurrence between fixed and mobile panels. Relative importance was assigned to each variable and data were combined in mathematical models used to determine how a user might perceive a given power plant landscape. Factors such as color of panels, surrounding flora and layout were important to the public.  It was shown that the model was able to match preferences well by giving positive or negative values to several criteria.

Models of this sort and further study will be helpful in determining the visual impacts solar power plants have on people. Perception is very important when matters involve public approval and that may be the case for solar plants. Knowing what appeals to the eye will help developers build the most pleasant systems possible and fewer citizens might complain that a solar power plant has ruined the view.   

Prospective Combined Solar—Wind Energy

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Renewable energy sources are certainly big considerations for our generation, but their economic feasibility remains in question, even the most well studied—wind and solar energy. Wind and solar energy are two big renewable energy options. Wind energy is currently much less expensive at 7.5681 c€/kWh than photovoltaics at 43.1486 c€/kWh.  Dufo-Lopez et al. (2009) examine the feasibility of a combined solar-wind energy production system in Spain in three different forms.  Type A in which all energy is sold to the grid; Type B in which some energy is sold to the grid and some is used to produce hydrogen which is also sold; 3rd Type C in which some energy is sold to the grid, some used to produce hydrogen later used in a fuel cell and the electrical energy thus generated is sold.  It was found that the intermittent production of hydrogen was only economical in areas with a high wind speed and if the selling price was at least 10 c€/kWh, much higher than currently allowed under Spanish law.— Teija Mortvedt 
Dufo-Lopez, R., Bernal-Agustin, J.L., Mendoza, F., 2009, Design and Economical Analysis of Hybrid PV-wind Systems Connected to the Grid for the Intermittent Production of Hydrogen, Energy Police 37, 3082–2095.  

   Wind energy would be much less expensive to produce in Spain because of equipment costs, but wind speeds can vary greatly within much of the land that has been determined to have a high enough wind speed is already occupied by wind installations.

Conversely photovoltaics can be installed almost anywhere because solar irradiation does not vary much within a geographical area considered. Economically it makes sense to combine the two technologies because wind power will help bring down costs and solar energy will make for a larger area of production.
The three types of hybrid PV-wind systems considered vary the degree to which hydrogen is used.  In type B and C systems hydrogen will be generated when the excess energy generated from the electrical systems exceeds the evacuation capacity of the electrical grid. Models B and C are a viable option only if wind speed is high enough, and therefore  geographically limited. this can only be implemented in certain areas of Spain. Other wish PV only systems are the best option for places with sub par wind levels.

Solar energy is an overall economically feasible option to supply U.S. energy needs

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Solar energy is currently only a minor contributor to  U.S. renewable energy options due to cost and intermittency issues.  But advances in technology have  led to drastic cost reductions in the production of photovoltaics (PV). Such advancements open the door for solar energy to become cost competitive with fossil fuels by 2020 (Fthenakis et all. 2009).  The issue of intermittency can be solved by integrating PV with compressed air energy storage (CAES) and enhancing thermal storage capabilities.  Even under the worst weather conditions it is shown that solar energy has the capacity to supply 69% of the total electricity needs of the U.S. by 2050 and over 90% by 2100. Advances in technology make solar energy a promising renewable energy source.  The challenge will be securing enough political foresight to realize this potential.— Teija Mortvedt
Fthenakis, V., Mason, J. E., Zweibel, k., 2009. The technical, geographical, and economic feasibility for solar energy to supply the energy needs of the U.S., Energy  Policy 37, 387–399.

Vasilis Fthenakis and colleagues have used current data and figures to forecast future energy demand levels in the U.S. and then extrapolated the deployment level of existing solar technologies in order to prove the feasibility of solar energy as a dependable cost effective resource.
With technology comes efficiency in PV production leading to cost reduction.  Module layers can be made thinner to require less material in their production and horizontally merging input production at onsite PV power plants will also decrease cost. Compressed air energy storage will ensure that even on a cloudy day, base level energy needs will still be met because energy is over–produced during sunny periods and stored with CAES. Concentrating solar power (CSP) systems offer a viable option for thermal energy storage if consistent annual deployment takes place resulting lowered costs.
The southwest (SW) United States is ideal for solar energy production.  At least 640,000 km2 (250,000 square miles) of land is suitable for solar power plant construction in this area. The SW receives over 6.4 kWh/m2 day and 4,500 Q-Btu per year, and a mere 2.5% of this yearly solar radiation equates to the current annual U.S. energy consumption. But production in the SW would require a national transmission network using high capacity lines.
Solar plants must be oversized in order to meet both peak energy needs and base-load solar levels.  However this will result in excess energy output, enough to easily allow hydrogen production during the spring, summer and fall months. This would allow the hydrogen transportation market to open up as a supplement to biofuels.

Technology is growing and will likely continue to do so at a steady to increasing pace.  So advancements are of little worry compared to the political factors involved in the implementation of these alternative energy sources.  Political planning and foresight will be invaluable to the advancement of solar energy utilization