Category CONGRESS

PAST SOLAR THERMAL PROJECTS

In Hawaii, three concentrating solar thermal projects, marked on Fig. 1, have gone through various stages of completion: solar repowering, a solar photovoltaic energy system; and a Small Community Solar Experiment at Molokai Electric Company. All were supported primarily by the

U. S. Department of Energy (USDOE), Hawaii state government, and through private cost­sharing.

The solar repowering project at Pioneer Sugar Mill Co., located in Lahaina on the leeward (dry side) lowlands of West Maui, called for a preliminary design of a solar power tower adjacent to the sugar factory. This concept featured a field of mirrors or heliostats directing sunlight to a centrally located receiver for steam production for use in the sugar milling process and power generation...

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SOLAR THERMAL DEVELOPMENTS IN HAWAII

Arthur Seki1 and Patrick Takahashi2

Hawaiian Electric Company, 820 Ward Avenue, Honolulu, Hawaii 96814-2109
2Hawaii Natural Energy Institute, 2540 Dole Street, Holmes Hall 246, Honolulu, Hawaii 98622

ABSTRACT

From the late 1970s to the early 1980s, a number of solar thermal projects were designed and operated in Hawaii, including a power tower concept designed for Maui, a parabolic trough photovoltaic/thermal system operated on Kauai, and a parabolic dish system designed for Molokai. Descriptions of these projects are provided. A preliminary assessment of potential solar thermal sites in Hawaii has been made, and the solar insolation data used in this assessment are presented. A summary of recent solar thermal energy developments in Hawaii will be made...

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FUTURE PLANTS

Existing contracts with Southern California Edison call for three additional large solar plants totalling 240 MWe. In addition, an 80-MW SO#2 contract with San Diego Gas & Electric Co. will result in the thirteenth SEGS plant. All of these facilities will be developed by LUZ and owned by private investors. These plants are planned to be constructed in the 1991-1994 time period.

It is also likely that by the mid-1990’s several SEGS plants will be constructed with utility ownership. It is expected that these plants will have capacities over 80 MWe and possibly as high as 200 MWe. Burgeoning environmental concerns, the gaining recognition of SEGS plants as a reliable power source and competitive costing are a few of the major reasons leading to this possibility...

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PERFORMANCE

Since the facilities are investor-owned, performance is measured first in revenues and second in MWh produced. A key aspect of these facilities is the ten-year performance warranty given by LUZ to the owners. Plant performance is routinely evaluated not only in absolute terms but also relative to original projections. The power purchase agreement defines time-of-use electricity rates which place very high values on electricity produced in the on-peak period during summer weekday afternoons from 12 pm to 6 pm for the months June through September. The summer mid-peak period – comprised of summer mornings and evenings – is next in importance, followed by winter mid-peak during winter weekday daytimes for October through May...

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SEGS TECHNOLOGY

The SEGS solar field incorporates line-focus parabolic trough collectors that collect and focus sunlight onto vacuum-insulated steel pipes. A heat transfer fluid (HTF) is circulated through the solar field where it is heated and supplied through a main header to the solar heat exchangers located in the power block. The solar-heated HTF generates superheated steam in a series of heat exchangers. The superheated steam is then fed to the high – pressure casing of a conventional steam turbine. The spent steam from the turbine is condensed in a standard condenser and returned to the heat exchangers via condensate and feedwater pumps to be transformed back into steam. After passing through the HTF side of the solar heat exchangers, cooled HTF is then recirculated through the solar field.

The LUZ...

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STATUS OF THE SEGS PLANTS

D. Kearney, H. Price, I. Replogle, T. Manes, J. Costanzo, Y, Gilon, S. Walzer Luz International Limited, Los Angeles, California, U. S.A.

ABSTRACT

Nine Solar Electric Generating Systems (SEGS) are now supplying 354 MWe peak power to the utility grid in Southern California. The facilities all utilize LUZ parabolic trough collectors matched with Rankine cycle steam power plants. With design solar-to-electric efficiencies of almost 23% and productions up to 0.53 MWh/m2 of solar field, the plants are generally operating well by standards of reliability and performance. The mature plants all achieved capacity factors of 100% or higher during the critical on-peak utility production period in 1990, with annual electric generation performance being dependent on the maturity of an individual plant...

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AMTEC using solar energy

If this efficiency is supposed for the combination of an AMTEC with e. g. a parabolic dish solar concentrator, the heat flow diagram figure 5 results. It shows that such a system has an efficiency of converting insolation to electricity comparable to a Stirling engine. In addition the waste heat is discharged with an interesting exergy.

/1/ T. K. Hunt, T. Cole

Research on the Sodium Heat Engine 13the Intersociety Energy Conversion Engineering Conf. 2011, Vol 3

/2/ Jarir Aktaa

Analyse der Umwandlungswirkungsgrade von AMTEC-Systemen unter verschiedenen Randbedingungen Diploma Thesis, University of Karlsruhe Institut for Reactor Technic, Dec 1989

/3/ F. Huber, V. Heinzel, W. Peppier, H. Will

AMTEC – A converter of thermal to electric energy KfK-Nachrichten

image542Fig...

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Efficiency calculation for experimental AMTEC – cells

AMTEC cells were operated in several laboratories worldwide. In some cases heat was converted into electricity and withdrawn from the cell with efficiencies of up to about 20% /1/.

Our institute started research on the AMTEC in order to exploit the manifold experiences with the sodium technology in combination with the activities in the field of energy systems. Parallel to the experimental work, the discrepancy of theoretical and experimental efficiency caused us to analyse the thermodynamics of the process and heat losses. The latter can be subdivided in losses owing to the process and those caused by the cell design. Figure 1 elucidates the effect of p3- pK on the energetic potential. p3 terminates the useful isothermal expansion. The sodium flows to

the condenser and condensates there...

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