Comfort Range Thermal Storage

The utility of incorporating substantial thermal storage capacity within the externally insulated shell of a residential structure, and within an arbitrarily selected Comfort Range (CR ~ 65–75 °F) is considered. Comfort Range Thermal Storage (CRTS) is found to increase the operating efficiencies of the broad range of generally considered heating and cooling sources. These include oil or gas-fires boilers or furnaces, air conditioners, heat pumps, solar collectors and (ambient) temperatures of opportunity. Composite building materials which incorporate components having large phase transition enthalpies in the CR are particularly advantageous. CRTS also supports effective space heating through use of architectural windows.     

Conservation vs. renewable energy: Cases studies from Hawaii

State of Hawaii generates about 90 percent of its electricity from imported fossil fuel sources. Thus, there is pressure from both public and policy makers to reduce the State dependency on foreign fossil fuel sources. To this extend, there are incentives created at State and Federal level for both residential and commercial buildings to install photovoltaic (PV) systems. Although such incentives are necessary for long-term objectives, it is shown in this study that retrofitting inefficient old building-equipment is another viable source to reduce the State of Hawaii's electricity demand. Four case studies are presented to illustrate that building-equipment retrofitting is a viable and necessary tool for increasing the energy efficiency of buildings. Each case study presents an equipment retrofit project electricity savings with its payback periods, and compares with equivalent electricity capacity and economics PV systems in Honolulu, Hawaii. The case studies show that energy savings from retrofit projects ranged from 28% to 61% for individual equipment retrofits. These results indicate that equipment retrofitting with energy-efficient alternatives is about 50% or more cost-effective than installing PV systems. This is so even when large renewable energy tax incentives provided by the Federal and State Governments are taken into account.     

A simplification of weather data to evaluate daily and monthly energy needs of residential buildings

Hourly, daily, monthly and annual heating and cooling requirements of a residential building located in Ottawa, Ontario, Canada were estimated, employing ENERPASS as the energy simulation tool, and performing hour-by-hour energy analysis. The following weather data were employed:

1. (i) Ten years (1967–1976) of weather data. The ten-year average of the results is identified as TYA.

2. (ii) A typical meteorological year (TMY) generated using the same ten years of data.

3. (iii) Two different hourly ambient air temperature distributions (T1 and T2) for a typical day in each month. The solar radiation on each surface was estimated using the mean monthly clearness index.

The house use patterns, including heat generation and the thermostat setting, were taken the same when using TYA, TMY, T1 or T2. The analysis was carried out for the house as it is (well insulated and airtight), and for two modifications: one with larger infiltration rate and lower wall thermal resistance, and the other with larger south-facing window area and using super-windows. The results of this study show that the long-range hourly, daily, monthly and annual heating and cooling requirements of a residential building located in a cold climate can be predicted by employing mean daily maximum and minimum temperatures and the mean monthly clearness index for each month. This amounts to substantial savings in computational costs, in either using many years of weather data or generating a TMY for the site. For locations lacking detailed hourly weather data, the use of data and the procedure outlined in this study may be employed to predict the long-range thermal performance of simple residential buildings.     

Applications of Thermal Energy Storage in Saudi Arabia

In Saudi Arabia, the heating, ventilating and air conditioning (HVAC) system typically accounts for 65% of the total electrical energy consumption in buildings. This is due to a very high ambient temperature which persists for a long period of time in a summer season. Moreover, gas turbines efficiency decrease also with the high ambient temperatures. In the HVAC industry cool storage, or commonly known as Thermal Energy Storage (TES) is the most preferred demand side management (DSM) technology for shifting cooling electrical demand from peak daytime periods to off‐peak night‐time. The most popular and well‐suited TES concept for Saudi Arabia is either chilled water or ice storage system, depending upon the applications and the required storage capacity. This paper shows how TES offers a means of reducing the electrical demand in large commercial buildings. Additionally, it is seen that efficiencies of the air cooled chillers are increased if they run overnight. Similarly efficiencies of gas turbine is also increased when a TES based pre‐cooled air is used as an inlet to the turbine. This paper also discusses favouring conditions and other aspects of cool storage applications in Saudi Arabia. TES economics are considered and a cost analysis is presented to illustrate the potential savings that can be achieved by the use of TES in Saudi Arabia. Copyright © 1999 John Wiley & Sons, Ltd.     

Heat planning for fossil-fuel-free district heating areas with extensive end-use heat savings: A case study of the Copenhagen district heating area in Denmark

The Danish government plans to make the Danish energy system to be completely free of fossil fuels by 2050 and that by 2035 the energy supply for buildings and electricity should be entirely based on renewable energy sources. To become independent from fossil fuels, it is necessary to reduce the energy consumption of the existing building stock, increase energy efficiency, and convert the present heat supply from fossil fuels to renewable energy sources. District heating is a sustainable way of providing space heating and domestic hot water to buildings in densely populated areas. This paper is a theoretical investigation of the district heating system in the Copenhagen area, in which heat conservation is related to the heat supply in buildings from an economic perspective. Supplying the existing building stock from low-temperature energy resources, e.g. geothermal heat, might lead to oversized heating plants that are too expensive to build in comparison with the potential energy savings in buildings. Long-term strategies for the existing building stock must ensure that costs are minimized and that investments in energy savings and new heating capacity are optimized and carried out at the right time.     

The use of waste heat in a solar still

There are instances in remote areas where heat is being wasted, e.g., in internal combustion, engines, etc. Some of this heat can be recovered to produce distilled water in solar stills.

The solar still replaces the cooling tower, ponds, or radiators normally used to control the engine temperature. The diesel cooling water in such a system remains separate from the saline water in the solar still.

The advantages of using such a system compared with a conventional solar still are:

1. (a) water costs are very much reduced

2. (b) the area occupied is much less, i.e., about 1/5th

3. (c) production has much less seasonal variation

4. (d) the efficiency of the solar still is improved due to the higher operating temperatures.

From experiments conducted at Highett using a Mk VI solar still fitted with a simple heat exchanger and a separate electrically-heated source of hot water to simulate the waste heat, design data are not available for application to working systems. The information required to match a solar still to a diesel's cooling requirement is:

1. (a) engine efficiency

2. (b) hourly fuel consumption

3. (c) hourly solar radiation

4. (d) hourly ambient temperatures.

A by-product of this work has been the production of a “solar water heater” which costs less than that of the cheapest conventional system. This “solar” hot water system uses a heat exchanger similar to what is used to transfer the waste heat to the saline water. It is envisaged to have hot water productions approximately the same as the distilled water productions. The influence of hot water production on the output of the waste heat solar still is discussed.     

Determination of free cooling potential: A case study for İstanbul,Turkey

A significant portion of energy consumed in buildings is attributed to energy usage by heating, ventilating and air conditioning (HVAC) systems. Free cooling is a good opportunity for energy savings in air conditioning systems. With free cooling, commonly is known economizer cycle, the benefits of lower ambient temperatures are utilized for a significant proportion of the year in many climates. The detailed analysis of local weather data is required to assess the benefits of economizer. In this study, free cooling potential of ?stanbul, Turkey was determined by using hourly dry-bulb temperatures measurements during a period of 16 years. It is found that the free cooling potential varies with supply air temperature and months. It is determined that although there are substantial energy savings during a significant portion of the year especially in transition months (April, May, September and October), the high outdoor air temperatures from June to August, made the system not beneficial for free cooling except at high supply air temperature.     

How to achieve optimal and sustainable use of the subsurface for Aquifer Thermal Energy Storage

A heat pump combined with Aquifer Thermal Energy Storage (ATES) has high potential in efficiently and sustainably providing thermal energy for space heating and cooling. This makes the subsurface, including its groundwater, of crucial importance for primary energy savings. The regulation of ATES systems is similar in many countries around the world. This paper seeks solutions for the institutional hindrances to the diffusion of ATES. The use of aquifers by individual ATES systems can be optimized to maximize their efficiency on the one hand, and to optimize the performance of the regional subsurface for energy storage on the other. The application of ATES in an aquifer has similar properties as other common resource pool problems. Only with detailed information and feedback about the actual subsurface status, a network of ATES systems can work towards an optimum for both the subsurface and buildings, instead of striving for a local optimum for individual buildings. Future governance of the subsurface may include the self-organization or self-governance. For that the ATES systems need a complementary framework; interpretation of interaction, feedback and adaptable and dynamic control interpretations are the key elements for the optimal and sustainable use of the subsurface.     

Energy and economic analysis of an integrated solar absorption cooling and heating system in different building types and climates

The use of solar energy in buildings is an important contribution for the reduction of fossil fuel consumption and harmful emissions to the environment. Solar thermal cooling systems are still in their infancy regarding practical applications, although the technology is sufficiently developed for a number of years. In many cases, their application has been conditioned by the lack of integration between cooling and heating systems. This study aims to evaluate the potential of integrated solar absorption cooling and heating systems for building applications. The TRNSYS software tool was used as a basis for assessment. Different building types were considered: residential, office and hotel. The TRNSYS models are able to run for a whole year (365 days), according to control rules (self-deciding whether to operate in heating or cooling modes), and with the possibility of combining cooling, heating and DHW applications. Three different locations and climates were considered: Berlin (Germany), Lisbon (Portugal), and Rome (Italy). Both energy and economic results are presented for all cases. The different local costs for energy (gas, electricity and water) were taken into account. Savings in CO₂ emissions were also assessed. An optimization of solar collector size and other system parameters was also analysed.     

Green energies and the environment

Globally, buildings are responsible for approximately 40% of the total world annual energy consumption. Most of this energy is for the provision of lighting, heating, cooling, and air conditioning. Increasing awareness of the environmental impact of CO₂ and NO_x emissions and CFCs triggered a renewed interest in environmentally friendly cooling, and heating technologies. Under the 1997 Montreal Protocol, governments agreed to phase out chemicals used as refrigerants that have the potential to destroy stratospheric ozone. It was therefore considered desirable to reduce energy consumption and decrease the rate of depletion of world energy reserves and pollution of the environment. This article discusses a comprehensive review of energy sources, environment and sustainable development. This includes all the renewable energy technologies, energy efficiency systems, energy conservation scenarios, energy savings and other mitigation measures necessary to reduce climate change.     

Determination of household energy using ‘fingerprints’ from energy billing data

Electric and gas utilities (in the U.S.A.) bill their customers on a regular basis, usually monthly or bimonthly. These data provide a truly valuable information resource for energy conservation programme analysts and evaluators. This paper discusses ways to analyse such billing data. The starting point is the Princeton University score-keeping model, which permits decomposition of total household energy use into its weather-and non-weather-sensitive elements; the weather-sensitive portion is assumed to be proportional to heating degree days. The score-keeping model also allows one to compute weather-adjusted energy consumption for each household based on its billing data and model parameters; this is the model's estimate of annual consumption under long-run weather conditions. The methods discussed here extend the score-keeping results to identify additional characteristics of household energy use. The methods classify households in terms of the intensity with which the particular fuel is used for space heating (primary heating fuel vs. supplemental heating fuel vs. no heating at all with the fuel). In addition, households that use the particular fuel for air conditioning are identified. In essence, the billing data and model results define household energy use ‘fingerprints’. The billing data and model results can also be used to identify and correct anomalous bills. Finally, the methods permit careful examination and analysis of changes in energy use from one year to another. They help explain why some households show anomalously large energy savings (e.g. they began using wood as a heating fuel during the second year) or negative energy savings (e.g. very high air conditioning energy use during the second year).     

Optimum storage of heat with a solar house

This paper reports calculations of the economic feasibility of solar house heating (and cooling) for different localities in the United States, and presents results in terms of maximum cost per square foot of solar collector which can be afforded if the solar system is to be competitive. Sunny mountainous regions, with cold winters (large fuel bills to be saved) are the most favorable areas.

Particular attention is given to the efficiency and capacity of energy storage and to the possibilities of saving summer heat for winter use. It is found that long-term storage is less economical than short-term storage. Storage costs of about a dollar per therm (10⁵ Btu), or solar collectors built and installed for $1.50 per sq ft, would make solar houses commercially competitive.     

A comprehensive review of solar thermoelectric cooling systems

The negative environmental impacts of burning fossil fuels have forced the energy research community seriously to consider renewable sources, such as naturally available solar energy. This paper provides an overview of solar thermoelectric (TE) cooling systems. Thus, this review presents the details referring to TE cooling parameters and formulations of the performance indicators and focuses on the development of TE cooling systems in recent decade with particular attention on advances in materials and modeling and design approaches. Additionally, the TE cooling applications have been also reviewed in aspects of electronic cooling, domestic refrigeration, air conditioning, and power generation. Finally, the possibility of solar TE cooling technologies application in “nearly zero” energy buildings is briefly discussed, and some future research directions are included. This research shows that TE cooling systems have advantages over conventional cooling devices, including compact in size, light in weight, high reliability, no mechanical moving parts, no working fluid, being powered by direct current, and easily switching between cooling and heating modes.     

Comfort criteria for passively cooled buildings a pascool task

The application of passive cooling techniques to buildings in warm climates creates the need for appropriate comfort criteria. Conventional comfort criteria, usually based upon laboratory experiments, seem to be unnecessarily severe. The paper describes preliminary findings of the PASCOOL Thermal Comfort task which, responding to renewed interest in behavioural aspets of thermal comfort, sets out to establish appropriate limits by field studies and theoretical considerations.     

Solar radiation calculation methodology for building exterior surfaces

The present article shows a new methodology of calculation of the direct, diffuse and reflected incident solar radiation, in all type of surfaces, either in open urban environments or inside buildings. This methodology is applicable in problems related to solar access (space heating in buildings, shadowing of open spaces), solar gains (space cooling in buildings), and daylighting. Solar radiation is the most important contribution to the surface and volumetric energy balance during the daytime. Particularly, solar radiation is the main contributor to heat gains in buildings, especially in residential buildings, where internal gains are very low. Utilization of daylight in buildings may result in significant savings in electricity consumption for lighting while creating a higher quality indoor environment. Additional energy savings may also be realized during cooling season, when reduction of internal heat gains due to electric lighting results in a corresponding reduction of cooling energy consumption.The analysis of the existing calculation methods and proposed in the scientific bibliography for the calculation of the solar radiation in problems of solar access in winter, solar gains in summer, and daylighting, takes us to the necessity of outlining a new and complete methodology. This new methodology is applicable to all these problems with a great accuracy and calculation speed.     

Solar operated absorption air-conditioner for a Kufra house

The use of solar energy for domestic water heating and space heating has proved to be viable. Space cooling is another promising avenue for utilization of solar energy. Solar operated absorption air-conditioning systems, in different situations, have been found to be feasible. Such systems can make use of the expensive collectors which are, in any case, installed for water and space heating.

In this paper the cooling of a prototype house, in Kufra, is reported. Starting with measured radiation and ambient data, calculations are performed on an hourly basis to determine the cooling load, radiation in the collector plane, heat delivered by the collectors and the heat stored in or discharged from the storage tank. Three different types of collectors with varying efficiencies are considered. These collectors are of the evacuated tube, selective coated and black painted types. The study confirms that the water-lithium bromide absorption system can provide summer air conditioning in arid zones of Jamahiriya where there are diffuclties with the supply of electricity and fossil fuels.     

Different strategies for operation of flat-plate solar collectors

Three strategies for solar collector operation are defined. These involve keeping one of the following constant during the day:

1. (i) the average working fluid temperature,

2. (ii) the outlet temperature and

3. (iii) the inlet temperature.

A graphical and analytical method previously developed by the authors was generalized to analyse and compare these strategies. For a constant flow rate, the best strategy is to maintain a constant inlet temperature. A constant outlet temperature is recommended when flow-rate control is possible.     

公共建筑空调冷热源工程适用性的调查分析

对我国不同气候区6个城市的96栋公共建筑空调冷热源状况进行了调研.目前我国公共建筑的空调冷源主要以电为能源的蒸汽压缩式制冷冷水机组,以燃油和燃气为能源的溴化锂吸收式冷热水机组、各种类型的热泵机组也占有一定的比例,蓄冷技术和区域供冷技术应用不多.建筑类型决定了其使用功能,气候条件决定建筑的使用环境条件,均会影响空调冷热源...     

Integration of trigeneration system and thermal storage under demand uncertainties

In a commercial building, a large portion of electricity is usually consumed in air conditioning to control indoor-air temperature and humidity. Energy savings or efficient production in air conditioning system is, therefore, crucial. In recent years, trigeneration systems, which provide electricity, heating and cooling, and thermal storage systems, which temporarily store cooling energy to smooth its production pattern, are attracting more attentions. These systems with different operating principles are usually designed based on nominal or peak loadings. With altering seasonal or day/night cooling demands, the performance and overall economics of the design may deprive.     

Reducing energy use in the buildings sector: measures, costs, and examples

This paper reviews the literature concerning the energy savings that can be achieved through optimized building shape and form, improved building envelopes, improved efficiencies of individual energy-using devices, alternative energy using systems in buildings, and through enlightened occupant behavior and operation of building systems. Cost information is also provided. Both new buildings and retrofits are discussed. Energy-relevant characteristics of the building envelope include window-to-wall ratios, insulation levels of the walls and roof, thermal resistance and solar heat gain coefficient of windows, degree of air tightness to prevent unwanted exchange of air between the inside and outside, and presence or absence of operable windows that connect to pathways for passive ventilation. Provision of a high-performance envelope is the single most important factor in the design of low-energy buildings, not only because it reduces the heating and cooling loads that the mechanical system must satisfy but also because it permits alternative (and low-energy) systems for meeting the reduced loads. In many cases, equipment with significantly greater efficiency than is currently used is available. However, the savings available through better and alternative energy-using systems (such as alternative heating, ventilation, cooling, and lighting systems) are generally much larger than the savings that can be achieved by using more efficient devices (such as boilers, fans, chillers, and lamps). Because improved building envelopes and improved building systems reduce the need for mechanical heating and cooling equipment, buildings with dramatically lower energy use (50–75% savings) often entail no greater construction cost than conventional design while yielding significant annual energy-cost savings.