The Van Geet home near Denver, Colorado, demonstrates the successful integration of energy conservation measures and renewable energy supply in a beautiful, comfortable, energy-efficient, 295-m 2 (3,176-ft 2 ) off-grid home in a cold, sunny climate. Features include a tight envelope, energy-efficient appliances, passive solar heating (direct gain and Trombe wall), natural cooling, solar hot water, and photovoltaics. In addition to describing this house and its performance, this paper describes the recommended design process of (1) setting a goal for energy efficiency at the outset, (2) applying rules of thumb, and (3) using computer simulation to fine-tune the design. Performance monitoring and computer simulation are combined for the best possible analysis of energy performance. In this case, energy savings are estimated as 89% heating and cooling, 83% electrical, and nearly 100% domestic water heating. The heating and cooling energy use is 8.96 kJ/°C·day·m 2 (0.44 Btu/°F·day·ft 2 ).

As interest for clean renewable electric power technologies grows, a number of parabolic trough power plants of various configurations are being considered for deployment around the globe. It is essential that plant designs be optimized for each specific application. The optimum design must consider the capital cost, operations and maintenance cost, annual generation, financial requirements, and time-of-use value of the power generated. Developers require the tools for evaluating tradeoffs between these various project elements. This paper provides an overview of a computer model that is being used by scientists and developers to evaluate the tradeoff between cost, performance, and economic parameters for parabolic trough solar power plant technologies. An example is included which shows how this model has been used for a thermal storage design optimization.

Even though there are a number of examples of BIPV, the concept of integration into the building and its design process have not yet been clearly defined. Lack of integration makes this new technology application expensive and very complex to implement. The challenge is how to make this new concept easily applicable and to spread this promising technology for users. In order for PV technology to be added effectively into the design process, full integration is essential. Full integration can be achieved when close interface develops between the PV System and the elements of the building design process. The design process is the spine that links the building from its inception all through its life cycle. The architects, along with the consultants and technical experts, are directly responsible for this process. PV has to be part of the building material and its building material properties have to be equivalent to other conventional building materials. PV has to fit into the building design process from the beginning. As a building component, it has to have certain standards and codes that will fit well within general building codes. This paper starts with the definition of the architectural building design process. It then continues with identifying the barriers that have direct effect on this process. These barriers are lack of interface (integration with typical building process), lack of common language, mismatched potential, unknown performance, and lack of economic analysis. The paper concludes by giving suggestions on how these barriers can be broken.

This paper presents results from a project sponsored by the California Energy Commission that involved the design and testing of an augmented generator for a solar fired, double effect absorption chiller. Solar powered absorption chillers use water heated by an array of solar collectors to boil a solution of lithium bromide and water. The energy transfer process between pressurized water heated by the solar collectors and the LiBr/H 2 O solution is the focus of this study. A method of augmenting the heat transfer in the generator was developed, bench tested and implemented in an operating 70kW solar HVAC system. The augmented design involved installing twisted stainless steel inserts in the tubes where the LiBr/H 2 O solution boils and refrigerant vapor is generated. The inserts increased the overall heat transfer coefficient between the heat medium in the shell side of the generator and the LiBr/H 2 O solution in the tubes. A solar-fired, double effect absorption chiller requires the collector array and storage tank to operate at temperatures in excess of 150°C. At these temperatures, the heating water must be at a pressure of about 700kPa to prevent it from boiling. This combination of high temperature and high pressure requires that the collectors, storage tanks, pumps, valves and piping be designed according to pressure vessel codes. This increases the initial cost of the system and also requires significant maintenance. The main objective of this work is to develop a method of lowering the requirements for a 150°C heating medium. The ultimate goal is to operate at about 120°C while maintaining the Coefficient of Performance and cooling capacity of the absorption chiller. The results presented in this paper show that the generator with twisted inserts can operate with an average log mean temperature difference of 10°C. The average COP of the chiller is about 1.0 and the chiller provided all of the cooling required by a 743 m 2 building. Without the twisted inserts, the generator operated with a temperature difference of 22 to 28°C. The inserts provide significant reduction in the operating temperature of the solar collectors and do not adversely affect the performance of the double effect absorption chiller.

We report on the performance of a new hybrid luminaire designed to blend light from a fiber optic solar source with electric fluorescent lamps. The luminaire design studied involves a commercially-available fluorescent luminaire that had been modified to include optical elements for efficiently dispersing a fiber optic solar light source. Quantitative measurements of the hybrid luminaire’s optical efficiency and spatial intensity distribution/deviations are discussed. The effects of static differences and dynamic fluctuations in spatial intensity distribution are qualitatively discussed and potential design improvements examined.

The first commercial-scale Duke Solar Power Roof™, a roof-integrated solar cooling and heating system, began operation in Raleigh, North Carolina in late July 2002. This system is designed to provide 176 kW (50 ton) of solar-driven space cooling using a unique nonimaging concentrating solar collector. The measured performance of the system during its first months of operation is reported here, along with a description of the design and operation of this system.

Commercially available photovoltaic (PV) modules and systems often fall short of meeting the performance ratings specified by the module manufacturers or system designers [1]. This has resulted in reduced performance and low system availability, some system failures, and generally, a lack of confidence by systems users. Hence, a need for an independent accredited laboratory to conduct the testing and certification of PV modules and systems has been indicated by the PV industry, electric utilities, and other system users and owners. To meet this industry and user need, the Florida Solar Energy Center (FSEC) has started a PV testing and certification program. The FSEC PV testing laboratory and certification program have been accredited by the American Association for Laboratory Accreditation (A2LA) and approved by the PowerMark Corporation (PMC, www.powermark.org ), which is the certification body of the PV industry in the United States. The FSEC program currently covers three areas: (i) PV module power rating certification, (ii) Stand-Alone PV system performance evaluation and certification, and (iii) Grid-Connected PV system design review and approval. The PV module power rating certification is central to these three areas of the FSEC program, as illustrated in Figure 1. The details of the FSEC PV testing laboratory accreditation and certification program are described in a previous paper [2].

The United States Army’s Soldier Tactical Mission System is capable of providing a dramatic change in small-unit warfare with its enhanced communications, situational awareness, and navigation capabilities. A significant drawback to this system, however, is that the very systems that provide these advantages to the soldier also demand high quantities of energy. In order to design an adequate energy delivery system to support the operation of the soldier’s enhanced equipment, the problem is broken down and analyzed into three general areas: energy demand, energy management, and energy source design. The aim of this paper is to introduce the reader to each of these three general areas, thereby providing a potential catalyst for future research and exploration into the design solution of adequate energy delivery systems.

The Florida Solar Energy Center has been accredited by both the American Association for Laboratory Accreditation and PowerMark Corporation to certify grid-tied photovoltaic systems. The certification process involves both the testing of photovoltaic modules for performance ratings and the review and approval of system designs to provide photovoltaic system design certification. This paper focuses on the design review and approval process, which consists of a documentation review and focuses on the completeness and accuracy of instructions, schematics, and accompanying materials. System designers have received substantive critiques and assistance through the third-party technical reviews used in this process. As a result, photovoltaic system manuals that accompany reviewed systems lead to a greater likelihood of code-compliant and high-performing installations.

Amonix has designed, manufactured, installed, and tested over 500 kW of high concentrating PV systems based around a concentrating silicon cell that set a new world efficiency record in 1992. This paper describes the development of this product as well as the physical and operating characteristics of the system. The operating characteristics that make this system attractive for grid, distributed, and off-grid are discussed. Data is presented that demonstrates the high daily power generating capability and the energy performance of the concentrating PV system. Other attributes of the system are also discussed such as the automatic/unattended operation, the short installation time, etc. An array installed at Pomona, CA is described, it has operated unattended for over 3 years and is still producing power today.

Emergency diesel generators in outdoor enclosures use large amounts of electric resistance heat to keep the engines warm all year. The heat is delivered to the jacket water of the engine by means of an electric resistance cartridge heater. For mid sized generators (150 KW – 1,000 KW) the annual electric use to deliver 130 degree F water can be 10,000 to 30,000 kwhr in a climate zone with 4,000 heating degree days (65 F base). An alternative to electric heating of the jacket water, is to solar heat the enclosure with 110 F air. This reduces the heat loss from the engine and therefore reduces the demand on the electric resistance heater. The paper describes the opportunity for solar air heating of emergency generators and the design and construction of two ground mounted systems and one solar heating building at the US Geological Survey in Reston, VA.

One of the main problems when designing a solar thermal power plant is to find the optimal parabolic trough field size. Errors made in this context can easily lead into a financial disaster. Simulation tools that handle all aspects of a power plant (technical as well as economical) treat such economical problems as a whole and can be very helpful during the design process. However, even the smartest simulation tool depends significantly on the input parameters, such as the solar irradiance. As a result of the given considerations a new method for estimating the solar field size as a function of the solar irradiance is proposed. Additionally, this paper demonstrates a path to simulate the complexity of a parabolic trough power plant.

Metal hydrides have been investigated for use in a number of solar thermal energy applications, such as heat regenerators or hydrogen storage technology, but rarely for thermal actuators. Preliminary experimental results from a prototype solar thermal metal hydride actuator, using copper-encapsulated porous metal hydride compacts of LaNi 5 , indicate that this thermal-mechanical system can produce high specific forces (over 100 (N/g) ), with response times on the order of seconds. These operational characteristics, along with features such as being bio-mimetic, compact, operationally safe, lubricationless, noiseless, soft actuating, and environmentally benign, result in an actuator that is ideal for many industrial, space, defense, and biomedical applications. In this paper, we report recent work directed toward predicting and characterizing the performance bounds of the actuator, specically concentrating on elements which might comprise an actuator driven by concentrated solar radiation. A complete solution of the 1D governing heat and mass transfer equations with an ideally selective reactor surface are used to predict bounds on performance in terms of volume flow rates and realistic actuation times. The advantages and disadvantages of the design are discussed from this perspective. The preliminary data show a great potential for these metal hydride actuators to be used for solar thermo-mechanical applications.

The design of a nonimaging secondary reflector as part of a parabolic trough receiver has been developed and evaluated. A detailed optical model was used for evaluation, which offered insight into the optical performance of the secondary and showed that the design offers about a 1% net increase in optical efficiency. In addition, the secondary was estimated to reduce heat loss from a high-performance evacuated receiver by about 4%. Overall, the net performance advantage of the secondary reflector is calculated to be 1.4%, that is, the entire trough collector field would have a 1.4% greater annual thermal energy output. This performance increase is small, but the non-imaging secondary also achieves other indirect benefits such as better flux uniformity around the absorber tube, and increased tolerance of parabolic trough collectors to optical errors.

The solar chimney is a simple renewable energy source consisting of three main components, a solar collector, chimney and turbine. Air under the collector is heated by the greenhouse effect. This less dense air rises up a chimney at the collector centre and drives an electricity-generating turbine. The operation of a solar chimney power plant is simple but high component efficiencies are needed for successful operation. A turbine design based on the design requirements for a full-scale solar chimney power plant is presented. The design integrates the turbine with the chimney. It is proposed that the chimney base legs be offset radially to act as inlet guide vanes and introduce pre-whirl before the rotor to reduce the exit kinetic energy. A three-step turbine design method is presented. A free vortex analysis method is used to determine the major turbine dimensions. A matrix throughflow method predicts the flow path through the inlet guide vanes and rotor. Finally the blade profiles are design using an optimization scheme coupled to a surface vortex method to achieve blades of minimum chord and low drag. The proposed turbine design can extract over 80% of the power available in the flow.

A solar receiver-reactor concept for high-temperature thermochemical applications involving gas and condensed phases is presented. It features two cavities in series. The inner cavity is an enclosure, e.g. made of graphite, with a small aperture to let in concentrated solar power. It serves as the solar receiver, radiant absorber, and radiant emitter. The outer cavity is a well-insulated enclosure containing the inner cavity. It serves as the reaction chamber and is subjected to thermal radiation from the inner cavity. The advantages of such a two-cavity reactor concept are outlined. A radiation heat transfer analysis based on the radiosity enclosure theory is formulated and results are presented in the form of generic curves that indicate the design constraints. High energy absorption efficiency can be achieved by minimizing the aperture area, by maximizing the size of the inner cavity, and by constructing it from a material of high emissivity.

An experimental investigation of a solar chimney turbine design is undertaken. The aim of the program is to demonstrate and evaluate a proposed solar chimney turbine design. The measured results of an experimental model turbine are presented and the turbine efficiency calculated. The current turbine design has a total-to-total efficiency of 85–90% and total-to-static efficiency of 77–80% over the design range. Secondary objectives are to compare the measured and predicted results and through investigation of the experimental results suggest improvements to the turbine design.

A laptop by its virtue is a mobile apparatus therefore a power outlet may not necessarily be available to charge its batteries. Typical laptops have a range of up to two and a half hours of battery life under normal operation and some have as little as one and a half hours. Therefore for the computer user on the move it is important to have enough power available for more extended periods of time. Today’s technology provides a large number of other mobile appliances, instruments and tools that will also greatly benefit from extended power. Existing solar panels operate under direct sunlight conditions and are deployed only when the equipment is in use or stationary. The solar powered module developed at the Department of Mechanical Engineering, University of Puerto Rico – Mayaguez has the advantage that it recharges the laptop in transit even when it is not in operation. By charging the battery when it is stored it allows the battery to be recharged during a larger period of time therefore increasing the amount of energy stored. Different types of solar cells were tested under “real world” lighting situations in order to assess their potential for the intended application. The solar array was optimized for use under a larger range of illumination conditions such that it may operate when direct sunlight is not available. The ergonomic design is integrated into the laptop’s carrying case but it may also be detached and/or repositioned if desired. The solar panel is based on the latest technology of triple junction spectrum-splitting amorphous silicon solar cells. The equipment allows the use of a laptop or other portable equipment in situations when power is not available, therefore providing a needed service in remote locations to professionals in the field and provides a backup power source in the event of an emergency or lack of adequate infrastructure. The paper describes the design process in the selection of the solar cell technology used in the module.

Disasters, whether man-made or natural, destroy buildings, structures, lives and natural surroundings. As an example, Hurricane Andrew devastated South Florida with winds up to 140 miles per hour leaving more than 250,000 people homeless and severely damaging at least 85,000 buildings, in addition to traffic signals and other roadway devices. Traveling was hazardous with debris in the roadway, power lines down, traffic signals damaged or not working, and road signs missing. With so many traffic signals not working, normal traffic flow was disrupted and roadways became congested. The importance of maintaining traffic flow in a disaster was evident for effective movement of emergency vehicles and to support recovery efforts. The same effect is realized, but to a smaller degree, during brown-outs, severe storms, accidents and other power outages for whatever the cause. During power outages caused by disasters or other events, there are many traffic signals that are still functional, but not operational due to loss of electrical power. Recent advances in power electronics, lighting and alternative energy sources provide a means of making these functional traffic signals operational during power outages. Updating signal heads with new light emitting diode (LED) lamps will lower the energy consumption by 60 to 80 percent of that of existing incandescent lights. With lower power requirements, renewable energy sources such as photovoltaics, become capable of providing the needed electric power. Redesigning traffic signals to incorporate new low-energy technologies make renewables a more viable source of power. This paper addresses these issues with respect to energy consumption and describes a new design that uses renewables to power these new lighting technologies.

A new version of the ENERGY-10 computer program simulates the performance of photovoltaic systems, in addition to 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: a 16,000-ft 2 (1,487 m 2 ) office and laboratory building at the Smithsonian Astrophysical Laboratory in Hilo, Hawaii, and housing for visiting scientists [three 1400-ft 2 (130 m 2 ) and three 1564-ft 2 (145 m 2 ) houses] at the Smithsonian Environmental Research Center in Edgewater, Maryland. The paper describes the capabilities of the software, the method in which ENERGY-10 was used to assist in the design, and a synopsis of the results. The results indicate that ENERGY-10 is an effective tool for evaluating BIPV options very early in the building design process. By simulating both the building electrical load and simultaneous PV performance for each hour of the year, the ENERGY-10 program facilitates a highly accurate, integrated analysis.