Domestic Hot Water Usage Research Articles

Energy performance optimization for Army installations

Buildings contribute to a large fraction of energy usage worldwide. In the United States alone, buildings consume about 40% of total energy expenditure, including 71% of electricity and 54% of natural gas. 1 The Army alone spends more than US $1 billion for building-related energy expenses. The 2005 Energy Policy Act 2 requires that Federal facilities be built to achieve at least a 30% energy savings over the 2004 International Energy Code or ASHRAE Standard 90.1-2004, as appropriate, and that energy efficient designs must be life-cycle cost effective. According to the Energy Independence and Security Act (EISA 2007), 3 new buildings and buildings undergoing major renovations shall be designed to reduce consumption of energy generated off-site or on-site using fossil fuels, as compared with such energy consumption by a similar building in fiscal year 2003 (FY03) as measured by Commercial Buildings Energy Consumption Survey (CBECS) or Residential Energy Consumption Survey (RECS) data from the Energy Information Agency, by 55% in 2010, 80% by 2020, and 100% by 2030. Current US research efforts focus on renewable energy sources and single-building energy efficiency, and pay little attention to integration and minimization of energy use in building communities, i.e. Army installations and university campuses. There is no over arching ‘power delivery/energy storage/demand’ architecture and methodology to accomplish this. This article describes the Net Zero fossil fuel-based energy optimization process and illustrates it with an example based on the results of study conducted for a cluster of buildings at Fort Irwin, CA. Application of the energy optimization process to new construction and major retrofit project shows17–20 that use of high performance building envelope (improved insulation and air tightness), advanced lighting strategies, and efficient HVAC systems results in significant energy savings (site and source) in Army buildings in all climates. When buildings built or retrofitted with a high performance building envelope, using advanced lighting systems and highly efficient ‘low exergy’ HVAC systems, reach a theoretical energy use minimum, the largest percentage of the remaining energy use in the building will be related to its ‘mission’: lighting, plug loads, and domestic hot water usage. Additional savings may be achieved with measures related to improved efficiency of power generation supplied to the building (co- and tri-generation) and use of energy supplied from renewable energy sources. The integrated energy solution recommended here demonstrates that vastly improved energy efficiency and GHG reduction are feasible in the context of a normal scale development using proven approaches from the USA and elsewhere. Moreover, the optimization process can be applied to new construction and major renovation of buildings and building clusters projects developed for low energy communities.

Long-term monitoring and performance of ground source heat pumps

The results of a full annual cycle of detailed monitoring of ten domestic ground source heat pump systems installed in similar properties are presented. The monitoring scheme used was designed to allow full characterization of the system, including monitoring of the heat supplied by the pump to both space-heating and domestic hot water, and also monitoring of the energy consumption of the various heat pump constituents. This approach is contrasted with a more commonly adopted approach where seasonal performance factors (SPF) are obtained without invading the heat pump enclosure. A number of issues are discussed which can lead to significant inconsistencies in the latter approach. Quantitative differences in the SPF obtained by the two methods are calculated or estimated for the monitored systems. Generally, the simpler approach leads to underestimation of the SPF by an amount which is variable and dependent on factors such as domestic hot water usage, pump settings and precise meter locations. Sont présentés les résultats d'un cycle annuel complet de suivi détaillé de dix systèmes de pompes à chaleur géothermiques domestiques installés dans des propriétés similaires. Le plan de suivi utilisé a été conçu de façon à permettre une caractérisation complète du système, ceci incluant le suivi de la chaleur fournie par la pompe à la fois pour le chauffage des locaux et pour l'eau chaude à usage domestique, ainsi que le suivi de la consommation d'énergie des divers éléments des pompes à chaleur. Cette approche est mise en opposition avec une approche plus couramment adoptée dans laquelle les valeurs du coefficient de performance saisonnier (CSP) sont obtenues sans pénétration de l'enceinte de la pompe à chaleur. Il est discuté d'un certain nombre de problèmes qui peuvent conduire à des incohérences significatives dans la seconde approche. Les différences quantitatives du CSP obtenu selon les deux méthodes sont calculées ou estimées pour les systèmes suivis. En règle générale, l'approche la plus simple conduit à une sous-estimation du CSP dans une proportion qui est variable et dépend de facteurs tels que l'utilisation de l'eau chaude domestique, les réglages de la pompe et l'emplacement précis du compteur. Mots clés: performances énergétiques pompe à chaleur géothermique suivi coefficient de performance saisonnier (CPS) performances technologiques

Optimisation of minimum backup solar water heating system

Current flat plate solar water heaters overproduce slightly in summer and have poor performance in winter at the time of maximum load. They use an expensive absorber plate over the entire absorbing aperture of the collector and fail to use the backside of the absorber. They often have under insulated tanks and are not optimised as integrated systems. This paper describes a design approach taken to use existing commercial flat plate absorber and tank components in a new way to maximise solar contribution and minimise material usage in the construction of the system. The design criterion used is not maximum peak efficiency, but minimum annual backup energy supplied to the system to meet an annual load. This corresponds to meeting a minimum greenhouse emissions requirement in both invested pollution during manufacture and pollution from backup energy supplied. Two new designs are shown which allow the solar fraction of systems to be increased to approximately 80–90% in Sydney Australia using a standard model of domestic hot water usage specified in Australian Standard AS4234. Pollution from fuel use drops to as little as 40% of that of conventional flat plate solar water heaters. These new designs use one absorber plate instead of two and a smaller and better insulated tank. Comparisons of solar fraction are evaluated for a range of climatic conditions. An important insight is that with such a performance optimised system the ultimate solar fraction is limited by occasional long duration cloud cover at the site of installation and making the system larger only increases dumped energy, not utilisable energy. Technical efficiency improvements only reduce the required collector area. However, some additional backup fuel reductions can be made through manual control of backup energy use, because this allows finer control of backup relative to real demand. Pollution from backup fuel usage may be able to be reduced to 1/4 that of current flat plate solar water heaters.