Model calibration remains a significant topic for both researchers and practitioners in the HVAC field although calibrated building and air handling unit (AHU) models have been used for “measuring” building energy retrofit/commissioning savings, identifying operational problems, and optimizing system operation and control schedules for more than decades. This paper discusses the modeling and simplification of building and AHU systems used in the simplified model calibration process. The paper presents a two-level calibration procedure integrated with energy signatures for simplified building and AHU heating and cooling energy consumption models. The procedures are demonstrated using a detailed example. This procedure can be implemented into computer simulation programs to allow automatic calibration and fault detection in many HVAC engineering processes.

As unvented attics have become a more common design feature implemented by Building America partners in hot-dry climates of the United States, more attention has been focused on how this approach affects heating and cooling energy consumption. By eliminating the ridge and eave vents that circulate outside air through the attic in most new houses and by moving the insulation from the attic floor to the underside of the roof, an unvented attic becomes a semiconditioned space, creating a more benign environment for space conditioning ducts. An energy trade-off is made, however, because the additional surface area (and perhaps reduced insulation thickness) increases the building loss coefficient. Other advantages and disadvantages, unrelated to energy, must also be considered. This paper addresses the energy-related effects of unvented attics in hot-dry climates based on field testing and analysis conducted by the National Renewable Energy Laboratory.

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 ).

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.

This paper summarizes the results of three-year joint venture between the Northwest Energy Efficiency Alliance (Alliance) and Siemens Solar (SSI) to reduce electrical energy use of Czochralski (CZ) hotzones for growing silicon ingots used to make silicon solar cells. It also discusses a spin-off project with Advanced Silicon Materials LLC (ASiMI) to further reduce embedded energy by developing and certifying dendritic (teardrop) polycrystalline silicon (polysilicon) as an alternative feedstock to CZ rods or granular polysilicon. The first project saved over 50% (25 kilowatt-hours per kilogram) and reduced Argon gas consumption by 85%. The dendritic polysilicon project is expected to reduce process energy by 25% (another 50 to 63 kWh/kg). These two steps of the overall process normally consume 250 to 300 kWh/kg but now they will require only 175 to 200 kWh/kg, an overall reduction of 30%.

A study of cubic splines and Fourier series as interpolation techniques for filling in missing data in energy and meteorological time series is presented. The followed procedure created artificially missing points (pseudo-gaps) in measured data sets and was based on the local behavior of the data set around those pseudo-gaps. Five variants of the cubic spline technique and 12 variants of Fourier series were tested and compared with linear interpolation, for filling in gaps of 1 to 6 hours of data in 20 samples of energy use and weather data. Each of the samples is at least one year in length. The analysis showed that linear interpolation is superior to the spline and Fourier series techniques for filling in 1–6 hour gaps in time series dry bulb and dew point temperature data. For filling 1–6 hour gaps in building cooling and heating use, the Fourier series approach with 24 data points before and after each gap and six constants was found to be the most suitable. In cases where there are insufficient data points for the application of this approach, simple linear interpolation is recommended.

A simplified ice storage system model was developed in which the icemaking mode is reflected by a higher power consumption per unit cooling than in chilled-water mode. The performance of four control strategies for ice storage systems is evaluated. The four control strategies investigated are chiller-priority and constant-proportion as conventional, instantaneous controls, while storage-priority and optimal control represent sophisticated controls employing load forecasting. Six parameters were investigated with respect to their influence on the ice storage system performance: Storage losses, utility rate structures, rate periods, penalty for icemaking, storage capacity, and the impact of load forecasting. Optimal control was determined to provide maximal operating cost savings. The storage-priority control yields operating costs only slightly higher than those of optimal control. Chiller-priority control realized savings that were typically on the order of 50% of what is theoretically possible (optimal control). Constant-proportion control proved to be a simple control strategy yielding higher savings than chiller-priority, yet lower than storage-priority control.

This paper summarizes the results of a simulation analysis to determine the effectiveness of daylighting in reducing electrical energy consumption for office buildings in Egypt. Specifically, the impact on daylighting performance is investigated of window size, building size, daylighting control, and glazing type for three geographical locations in Egypt. It was determined that a window to wall area ratio of 0.20 minimizes the total annual electricity use for office buildings in three Egyptian locations, Cairo, Alexandria, and Aswan. A simplified analysis method is developed based on the analysis results to estimate the annual electrical energy savings attributed to daylighting.

An innovative secondary in-building pump system called the By-pass Blending Station (BBS) has been developed to reduce building pump energy consumption and maintain the desired return water temperatures in district heating and cooling systems. This method applies where district systems provide sufficient pump head for in-building water circulation. The BBS moves only the returned by-pass flow. Therefore, it uses less pump energy than the ASHRAE recommended method, which moves the entire building water flow by using in-building pump. The pump in the BBS is smaller than that of the ASHRAE recommended in-building secondary pump system. The BBS can be used in both constant and variable flow secondary systems. This paper compares the ASHRAE recommended secondary in-building pump with BBS systems using chilled water systems. The BBS only applies to cases where the primary distribution systems provide sufficient pump head for in-building circulation, which are typically found in commercial district cooling and heating systems.

In contrast to building energy conversion equipment, less improvement has been achieved in thermal energy distribution, storage and control systems in terms of energy efficiency and peak load reduction potential. Cooling of commercial buildings contributes significantly to the peak demand placed on an electrical utility grid. Time-of-use electricity rates are designed to encourage shifting of electrical loads to off-peak periods at night and weekends. Buildings can respond to these pricing signals by shifting cooling-related thermal loads either by precooling the building’s massive structure (passive storage) or by using active thermal energy storage systems such as ice storage. Recent theoretical and experimental work showed that the simultaneous utilization of active and passive building thermal storage inventory can save significant amounts of utility costs to the building operator, yet in many cases at the expense of increased electrical energy consumption. This article investigates an approach to ensure that a commercial building utilizing both thermal batteries does not incur excessive energy consumption. The model-based predictive building controller is modified to trade off energy cost against energy consumption. This work shows that buildings can be operated in a demand-responsive fashion to substantially reduce utility costs, however, at the expense of increased energy consumption. Placing a greater emphasis on energy consumption led to a reduction in the savings potential. In the limiting case of energy-optimal control, the reference control was replicated, i.e., if only energy consumption is of concern, neither active nor passive building thermal storage should be utilized. On the other hand, cost-optimal control suggests strongly utilizing both thermal storage inventories.

Accurate charge-control and state-of-charge monitoring of lead-acid batteries is an ever-increasing necessity in an industry that demands low-maintenance costs and highly available systems. If the batteries are charged by photovoltaic panels and are installed in remote sites (e.g. Oil sea-platforms, highway emergency bays, autonomous communications systems) and exposed to aggressive environmental conditions (e.g. Extreme temperature, high humidity), the problem of extending the batteries’ useful life becomes a challenge. Most charging algorithms do not perform well when photovoltaic panels are the sole source of energy because energy availability is not guaranteed. A charge algorithm that maximizes the use of energy generated by the panel during daylight hours is needed. This paper presents a microcontroller-based charge-controller suitable for photovoltaic applications. The controller performs temperature compensation on the charge algorithm. It also stores those parameters that provide an indication on batteries’ state-of-charge and state-of-health: Panel voltage, battery’s voltage and current, current demanded by a load and room temperature. The controller has serial communication capabilities that make possible the connection to a personal computer or central station. By using a local industrial network or radio links, multiple controllers can be monitored by a central station running a battery management program. The information collected by all the controllers in the system is analyzed to determine the state-of-charge of individual batteries and, if required, command the appropriate controller to perform special procedures like, for example, thorough diagnostics or equalization. Preliminary field-test results of a controller installed in a high-way emergency bay are presented in this paper. It is shown that protection against deep discharges is achieved, which contributes to extend the battery useful life.

This paper describes data and algorithms to estimate typical average interior illuminance from daylighting using a hybrid of Hay, Davies, Klucher, Reindl (HDKR) method for calculating total solar radiation on a tilted surface and the Illuminating Engineering Society (IES) Lumen Method for estimating interior illuminance from daylighting. This hybrid algorithm, in conjunction with typical meteorological data, directly accounts for shading and typical local cloud cover effects on an hour-by-hour basis, which is difficult to do using the IES sky-cover or sky-ratio methods. Several experiments show reasonable agreement between measured and calculated results. Case study examples demonstrate of use of the method, when incorporated into software, to quickly analyze daylighting potential in industrial facilities, and the use of this information to develop specific recommendations for cost-effectively reducing lighting energy use in industrial facilities by improving the utilization of natural lighting.

There is no common agreement on the use of balance valves in the most popular variable water flow systems. A comprehensive theoretical analysis has been conducted to investigate the impacts of balance valves on initial cost, pump operation power, and system control performance. The investigation finds that eliminating balance valves can (1) reduce 20% to 40% pump energy consumption in a typical variable flow water system; (2) reduce the maximum pressure drop across control valves; and (3) improve pump efficiency at most partial load conditions. The reduced pressure drop across control valves improve system control performance and may allow selecting some of the control valves at lower close-off pressure. Consequently, eliminating balancing valves can also potential reduce system initial costs.

As a nation the United States must reduce its dependence on imported energy resources. Net imports of foreign oil as a percentage of total U.S. oil demand have increased from 37% in 1980 to 55% in 2001 and are predicted to increase to 65% by the year 2016. Since heating and air conditioning account for 44% of the energy usage in a typical U.S. home, residential energy conservation techniques hold great promise for significant savings. Insulated concrete form (ICF) construction is a promising construction technique for both residential and commercial construction. Some advantages of ICF construction include: reduced construction time, compatibility with any inside or outside surface finish, insect resistance, strength, noise reduction, reduced infiltration, significant and continuing energy savings, lower HVAC capital costs for the building, and 12” (30 cm) wide window sills. Disadvantages of ICF construction include: resistance from builders and sub-contractors unfamiliar with the construction technique, higher material costs, the necessary custom window and door openings, and the difficulty and expense of making changes once the walls are in place. Even though the material costs are higher than typical (stick-frame) construction, labor savings might result in overall savings. In this paper actual energy usage for an ICF house constructed in 1998 is compared to the energy usage for a 1988 conventional stick-frame building. Comparison of these two buildings indicates a 75% reduction in energy usage per square foot per degree-day for the ICF building when compared to the stick-frame building. During this same time period, energy (gas) usage for heating and hot water decreased 85%. Computer simulations were made for both an ICF wall and for a conventional frame wall. These computer simulations indicate significant saving potential for the ICF wall when compared to a conventional frame wall section. In addition these simulations illustrate dramatically the effect of separating the thermal resistance and thermal capacitance inherent in this “sandwich” construction.

The traditional chilled water loop has been designed as a primary/secondary (P/S) system for several years. The primary loop maintains constant chilled water flow through the evaporator, and the secondary loop is designed as a variable flow system in response to variations in building cooling load. The primary/secondary design separates the chiller operation from the building load requirements. This design principle has been working adequately for old chillers that require constant chilled water flow to achieve stable chiller performance. However, these chillers operate inefficiently and consume unnecessary pump power. In recent years, the chiller industry has begun the use of variable water flow through evaporators. Significant energy savings can be achieved by using the variable flow principle. This paper compares the P/S system with variable chilled water system and also proposes an innovative solution: chilled water supply temperature reset to maintain the minimum chilled water flow and eliminate by-pass water flow. The energy consumption models including pump power and chiller compressor power improvement are presented to simulate the energy performance of two systems. ASHRAE detailed cooling coil models are also adopted to simulate the cooling coil discharge air humidity in order to verify the impacts of the chilled water supply temperature reset. Finally, a case study building demonstrates experimental results. Up to 10% pump and compressor power saving is demonstrated by simulations and the case study.

Las Vegas, Nevada, is one of the country’s most rapidly growing cities. To accommodate this growth, a great deal of home building takes place in Clark County, where the city is located. Builders can sell virtually as many houses as they can construct. All of these houses require utility services that, in general, have to be developed. These, of course, include water, electrical power and natural gas. With the high cooling loads required in this environment, the summer demand peaks for electricity are particularly severe. The emphasis of this paper was placed on the energy conservation methods for a planned zero energy residential home for the Southern Nevada area, which would enable net zero electric energy consumption from the local utilities over a year period. Although also important, the cost outcome of the project was considered a secondary issue. The energy analysis was arranged in three principal parts: • Reduction of heating and cooling loads through implementation of sound envelope construction. • Use of highly energy efficient A/C, gas furnace, and lights. • Solar control and utilization. The computer simulation package Energy 10 version 1.6 is employed during the envelope, A/C, furnace and energy-efficient light analysis. The software allows modeling and simulating of a buildings performance based on inputs such as geographical location, building type, orientation, construction materials used and others. The model selected for this study is reflective of the local construction practices, is a single-family one story, 1,610 ft residential house with north facing fac¸ade and an attached two-car garage, which in this paper is called the “Base Case”. As a result of the energy analysis performed in this paper, the low-energy house (Modified Case) was created. The Modified Case has the identical orientation and floor plan. Implementation of the full spectrum of energy conserving features yielded a dramatic 105% saving on the annual electrical energy consumption by the Modified Case house when compared to the house built according to the local practices. In addition, the space heating and space cooling energy consumptions were reduced by 96% and 72% respectively. Details of the simulations and the final design details are given in the paper.

The Laboratory Air Handling Unit (LAHU) system for laboratory buildings has been developed and optimized. Theoretical study has concluded that the LAHU with optimal outside air control and optimal heat recovery control significantly reduces thermal energy use, saves pump power consumption and improves office indoor air quality. This paper presents validation experiments of LAHU energy performance in a large university research building including detailed experimental methodology, procedures and preliminary experimental energy savings results. The experiments establish that the LAHU can reduce annual heating by over 30% and can reduce heat recovery pump power by over 50% for this typical laboratory building.

This investigation presents the thermal analysis of an experimental, low energy consuming home for low-income families, located in Puerto Rico, where the prevailing climate is hot and humid. The objective of this analysis is to aid in the design of energy efficient homes, which in turn will reduce energy consumption in the Island. This investigation compares the analysis of this experimental house, specifically designed for the tropics, to a similarly sized, conventionally built low-cost home. Different construction materials are evaluated in conjunction with the use of either natural ventilation or air conditioning. The impact of natural ventilation is analyzed, with results for the inside temperature and interior heat removal presented and compared. Additional energy saving strategies are evaluated, including solar thermal energy for domestic hot water production, daylighting and the use of energy efficient lights. The annual energy consumption of the proposed experimental home is calculated and compared with the energy consumption of the conventional house. The thermal load of the house is calculated through the use of mathematical simulations of the dynamic annual cooling load using well-known software such as Energy-Plus for a TMY for San Juan, Puerto Rico. Results for the inside temperature of the experimental house, the heat loss due to natural ventilation, the cooling load when air conditioning is used, and energy consumption are presented and compared with the conventional house. Results indicate that the experimental house is 30% more energy efficient when all the energy saving strategies are considered.

The Dual Receiver Concept presented in this paper improves the adaptation of the central receiver to the steam cycle in a solar thermal power plant. By combination of an open volumetric air heater and a tubular evaporator the Dual-Receiver Concept profits from the advantages of these two concepts while their characteristic problems are avoided. The water is evaporated directly in the tubular steam generator, preheating and superheating is done in heat exchangers by using the hot air from the volumetric receiver (Fig. 1). This paper presents a concept study that extends previous work on the 10 MW el level (Buck et al. 2004) to a level of 100 MW el which is the expected power range of future plants. The results confirm the benefits of the new concept, resulting from higher thermal efficiency of the receiver and lower parasitic power consumption. The annual mean efficiency is increased from 13% to 16%. Advantageous are also the reduced thermal loads in the receiver components.

In response to both global and local challenges, the University of Dayton is committed to building a net-zero energy student residence, called the Eco-house. A unique aspect of the Eco-house is the degree of student involvement; in accordance with UD’s mission, interdisciplinary student teams from mechanical engineering, civil engineering and the humanities are leading the design effort. This paper discusses the conceptual design of a net-zero energy use campus residence, and the analysis completed thus far. Energy use of current student houses is analyzed to provide a baseline and to identify energy saving opportunities. The use of the whole-system inside-out approach to guide the overall design is described. Using the inside-out method as a guide, the energy impacts of occupant behavior, appliances and lights, building envelope, energy distribution systems and primary energy conversion equipment are discussed. The design of solar thermal and solar photovoltaic systems to meet the hot water and electricity requirements of the house is described. Eco-house energy use is simulated and compared to the energy use of the existing houses. The analysis shows the total source energy requirements of the Eco-house could be reduced by about 340 mmBtu per year over older baseline houses, resulting in CO 2 emission reductions of about 54,000 lb per year and utility cost savings of about $3,000 per year. Detailed cost analysis and cost optimization have not been performed but are critical aspects of the UD Eco-house project, which will be performed in the future.