Andy Walker

Advances in Solar Buildings

In the autumn of 2002, 14 universities built solar houses on the National Mall in Washington, DC, in a student competition-the Solar Decathlon-demonstrating that homes can derive all the energy they need from the sun and celebrating advances in solar buildings. This paper describes recent progress in solar building technology that expands the designers palette and holds the potential to radically improve building energy performance. The discussion includes market conditions and solar resource data; design integration and modeling; window technology, daylighting, passive solar heating; solar water heating; solar ventilation air preheating; building-integrated photovoltaics; and solar cooling. The Solar Decathlon competition highlighted ways in which these strategies are integrated in successful solar buildings.

Performance Contracting for Parabolic Trough Solar Thermal Systems

Several applications of solar energy have proven viable in the energy marketplace, due to competitive technology and economic performance. One example is the parabolic trough solar collectors, which use focused solar energy to maximize efficiency and reduce material use in construction. Technical improvements are complemented by new business practices to make parabolic trough solar thermal systems technically and economically viable in an ever widening range of applications. Technical developments in materials and fabrication techniques reduce production cost and expand applications from swimming pool heating and service hot water, to higher-temperature applications such as absorption cooling and process steam. Simultaneously, new financing mechanisms such as a recently awarded US Department of Energy (DOE) Federal Energy Management Program (FEMP) indefinite quantity Energy Savings Performance Contract (Super ESPC) facilitate and streamline implementation of the technology in federal facilities such as prisons and military bases.

Analyzing Two Federal Building-Integrated Photovoltaics Projects Using ENERGY-10 Simulations

A new version of the ENERGY-10 computer program simulates the performance of photovoltaic (PV) systems and evaluates a wide range of opportunities to improve energy efficiency in buildings. This paper describes two test cases in which the beta release of ENERGY-10 version 1.4 was used to evaluate energy efficiency and building-integrated photovoltaics (BIPV) for two federal building projects: an office and laboratory building at the Smithsonian Astrophysical Laboratory (SAO) in Hilo. Hawaii, and housing for visiting scientists at the Smithsonian Environmental Research Center in Edgewater, Maryland. The capabilities of the software, the design assistance provided by ENERGY-10, and a synopsis of results are given. Estimates of annual energy delivery by the five PV arrays of the SAO are compared to F-Chart to help inform a validation of ENERGY-10. Results indicate that, by simulating both the building electrical load and simultaneous PV performance for each hour of the year, ENERGY-10 facilitates a highly accurate, integrated analysis useful early in the design process. The simulation is especially useful in calculating the effect of PV on the building peak load, and associated demand cost savings.

Performance of a Large Parabolic Trough Solar Water Heating System at Phoenix Federal Correctional Institution

At Phoenix Federal Correctional Institution in Arizona, the Federal Bureau of Prisons (FBP) completed a 1,584 m 2 (17,040 square feet) parabolic trough solar water heating system financed, installed and operated under an Energy Savings Performance Contract (ESPC) with Industrial Solar Technology Corp (IST). The ESPC was developed under a Cooperative Research and Development Agreement with the National Renewable Energy Laboratory (NREL). The system incorporates a 87 m 3 (23,000 gallon) storage tank. The system delivered 1,161,803 kWh (3,964 million Btu) of solar heat from March 1, 1999 to February 29, 2000. This energy would have cost

Evacuated Tube Heat Pipe Solar Collectors Applied to Recirculation Loop in a Federal Building: SSA Philadelphia

77,805.74 if purchased from the utility (based on the monthly average

An Heuristic Approach to Renewable Energy Optimization

/kWh cost). Sale of this energy to the prison provided

Wave Power for U.S. Coast Guard First District Lighthouses

70,025.18 in revenue to IST (a rate negotiated at 90 percent of the monthly average

Design and Analysis of a Large Solar Industrial Heat Plant for Frito Lay in Modesto California

/kWh utility cost). Thus, the prison saved

Time-of-Use Monitoring of U.S. Coast Guard Residential Water Heaters With and Without Solar Water Heating in Honolulu, HI

7,780.56 (the remaining 10 percent). A photograph of the collector system is presented in Figure 1. Results show that the system delivers heat reliably, with only minor operational problems which are listed and discussed. The system delivered a minimum of 80,315 kWh (274 Btu) in January 2000 to a maximum of 130,979 kWh (447 Million Btu) in October 1999. The prison pays IST for energy delivered by the solar system at a rate equal to 90 percent of the monthly average utility rate (10 percent guaranteed savings), over 20 years. Details of the establishment of the payment structure and the cost savings to the prison are discussed. Annual Emissions Savings are estimated by EPA multipliers [1] for Arizona as 627,374 kg/yr of CO 2 , 2,324 kg/yr of SO 2 and 2,297 kg/yr of NO x . Other benefits to the prison are also discussed, such as reduced operations and maintenance on the electric water heaters and a greater capacity to deliver hot water.

PV system “Availability” as a reliability metric — Improving standards, contract language and performance models

This paper describes design, simulation, construction and measured initial performance of a solar water heating system (360 Evacuated Heat-Pipe Collector tubes, 54 m 2 gross area, 36 m 2 net absorber area) installed at the top of the hot water recirculation loop in the Social Security Mid-Atlantic Center in Philadelphia. Water returning to the hot water storage tank is heated by the solar array when solar energy is available. This new approach, as opposed to the more conventional approach of preheating incoming water, is made possible by the thermal diode effect of heat pipes and low heat loss from evacuated tube solar collectors. The simplicity of this approach and its low installation costs makes the deployment of solar energy in existing commercial buildings more attractive, especially where the roof is far removed from the water heating system, which is often in the basement. Initial observed performance of the system is reported. Hourly simulation estimates annual energy delivery of 111 GJ/year of solar heat and that the annual efficiency (based on the 54 m 2 gross area) of the solar collectors is 41%, and that of the entire system including parasitic pump power, heat loss due to freeze protection, and heat loss from connecting piping is 34%. Annual average collector efficiency based on a net aperture area of 36 m 2 is 61.5% according to the hourly simulation.