Milton Keynes Energy Park revisited: Changes in internal temperatures and energy usage

A follow-up study was undertaken of 15 ‘low-energy’ dwellings in Milton Keynes, UK, that were originally monitored for temperature and energy consumption from 1989 to 1991. These measurements were repeated in 2005–2006, with the results compared with the baseline using standardised daily external conditions of 5 °C. The 2005–2006 study found mean temperatures of 19.8 °C (95% confidence interval: 19.7–20.5) for living rooms and 19.3 °C (CI: 19.6–20.1) for main bedrooms. Weak evidence was found for a 10% increase in gas consumption over 15 years to 87 kWh/day (95%CI: 77–96) and overall electricity usage rose by 30% to 15 kWh/day (CI: 13.6–16.5). Dwellings were classified into three groups of low, middle, and high-energy users in 1990. In 2005–2006, this high group consumed more energy than the other two groups combined and accounted for most increases in energy use; their gas usage rose by 20% to 130 kWh/day (110–150), electricity by 75% to 28 kWh/day (CI: 25.3–31.2), and had 50% higher energy intensity at 172 Wh/m² (CI: 150–195). On average the high group comprised dwellings that were larger, had been extended, and whose occupants had higher incomes than the two other groups. The results suggest that research for the development of energy policy, including building regulations, should focus both on how energy is currently used and on households where the largest future increases are likely to occur.     

Energy saving potential and strategies for electric lighting in future North European, low energy office buildings: A literature review

This article presents key energy use figures and explores the energy saving potential for electric lighting in office buildings based on a review of relevant literature, with special emphasis on a North European context. The review reveals that theoretical calculations, measurements in full-scale rooms and simulations with validated lighting programs indicate that an energy intensity of around 10 kWh/m² yr is a realistic target for office electric lighting in future low energy office buildings. This target would yield a significant reduction in energy intensity of at least 50% compared to the actual average electricity use for lighting (21 kWh/m² yr in Sweden). Strategies for reducing energy use for electric lighting are presented and discussed, which include: improvements in lamp, ballast and luminaire technology, use of task/ambient lighting, improvement in maintenance and utilization factor, reduction of maintained illuminance levels and total switch-on time, use of manual dimming and switch-off occupancy sensors. Strategies based on daylight harvesting are also presented and the relevant design aspects such as effects of window characteristics, properties of shading devices, reflectance of inner surfaces, ceiling and partition height are discussed.     

Application of overhangs and side fins to high-rise residential buildings in Hong Kong

For a typical lone high-rise 20-storey residential building in Hong Kong, the extent to which cooling of its 10th-floor (mid-level) rooms depends on overhangs and side fins was evaluated. By using the software EnergyPlus?, it was found that the application of overhangs would reduce the electricity consumption by up to 5.3%. The highest reduction was obtained in rooms with windows unshaded by own-wing walls, face west, and have 0.75 m overhangs. By using the same software, it was found that the application of side fins to the building with overhangs would reduce the electricity consumption by up to 1.4%, where the highest values belong to windows facing either north or south (at west wing), with out-of-core side fins.     

The potential of wastewater heat and exergy: Decentralized high-temperature recovery with a heat pump

There is a large potential in the heat losses from the wastewater leaving a building. We present a novel concept for recovering this heat. Instead of recovering it in a mixed state, the recovery immediately after use is evaluated. This allows the exploitation of the higher temperatures found at the points of warm water usage. By integrating a heat pump to utilize this heat, we can produce a higher temperature heat supply while maintaining a low temperature-lift requirement. This leads to the possibility of directly regenerating the hot water supply through wastewater heat recovery. The concept is a result of research into low exergy building systems, and is part of the IEA ECBCS Annex 49. We have modeled the annual performance of two different system scenarios, which result in a potential average annual coefficient of performance (COP) of over 6. The first scenario supplies up to 4400 kWh of heat for all hot water events with only 790 kWh of electricity, while the second scenario regenerated directly the hot water supply just for bathroom fixtures at 2400 kWh with just 410 kWh of energy. This is a significant reduction in the demand for hot water supply of a building compared to most modern installations.     

Identifying trends in the use of domestic appliances from household electricity consumption measurements

Results are presented from a monitoring study of the electricity consumption of a sample of UK domestic buildings. Five-minutely average whole house power consumption was recorded for 72 dwellings at five sites over a 2-year monitoring period. The mean annual electricity consumption for the households increased significantly by 4.5% (t = 1.9; p < 0.05, one-tailed) from the first to the second year of monitoring. New techniques are developed which estimate the electricity consumption of different appliance groups, based on analysis of the five-minutely monitored data. The overall increase in electricity consumption is attributed to a 10.2% increase in the consumption of ‘standby’ appliances (such as televisions and consumer electronics) and a 4.7% increase in the consumption of ‘active’ appliance (such as lighting, kettles and electric showers). The consumption of different energy user groups (low, medium and high) is also investigated and low and high users are identified as contributing to the overall increase in consumption. The need for further investigation, such as quantitative and qualitative studies, to improve understanding in domestic electricity consumption is discussed.     

Energy consumption and the potential of energy savings in Hellenic office buildings used as bank branches—A case study

Energy performance of non-residential buildings and in particular of office buildings used as bank branches is very limited. This paper presents new data from 39 representative bank branches and results from a more in-depth analysis of information from energy audits in 11 typical bank branches throughout Greece. The data was used to derive practical energy benchmarks and assess various energy conservation measures. Accordingly, the average annual total energy consumption is 345 kWh/m². The breakdown of the different end-uses reveals that HVAC averages 48% of the final energy consumption, lighting averages 35% and other office and electronic equipment average 17%. The most effective energy conservation measures reach annual energy savings of 56 kWh/m² by regulating the indoor set point temperature, while the use of HF electronic ballasts and CFL lamps may save about 22 kWh/m² and 29 kWh/m² with and without the use of the external marquee sign, respectively.     

Overcoming barriers to implementation of carbon reduction strategies in large commercial buildings in China

With an economic growth in GDP of around 10% per annum in recent years, energy consumption in the building sector in China now accounts for 25% of the total energy use in the whole nation. In large buildings in Beijing and Shanghai the consumption rate, at approximately 190 kWh/m² per annum, is around five times the energy use in residential buildings in those cities. Addressing this ever increasing energy consumption and the consequential green house gas (GHG) emissions must be a priority to achieve low carbon sustainability in China.     

Micro wind turbines in the UK domestic sector

The micro-scale wind turbine industry is expanding in the UK with institutional support and UK legislation encouraging the development of numerous companies with a profusion of design options. The application of micro wind turbines in urban environment is encouraged in the UK via a grant scheme which provides a proportion of the initial capital costs. This development is predicated on the assumption that micro wind turbines have the potential to reduce built environment CO₂ emissions. Current methods of estimating the wind speed are reported to over predict by approximately 2.0 m/s. The energy yields of a range of typical micro wind turbines (in the 0.4–2.5 kW size range) were estimated here using two wind speed datasets sited within 1 km of each other recorded with a temporal precision of 10 min. The annual energy yield of a 1.5 kW turbine was found to be 277 kWh and 2541 kWh for the two sites analysed indicating the problem with the current method of yield estimation. Between 33 and 55% of the electricity generated would be exported dependant on the dwelling's electrical demand. For the high yield site, the simple economic payback of this turbine was found to be 26.8 years i.e. beyond the likely life time of the turbine with CO₂ savings of 1093 kg CO₂. The research suggests that this technology does represent a possible route for reducing CO₂ emissions but this is unlikely to be realised unless an adequate method is found for more accurately predicting energy yield at a specific site.     

Improved airflow around multiple rows of buildings in hot arid climates

This paper studies the natural wind environments in two locations of hot climate regions at Egypt. Aswan and Farafra in south and west Egypt were selected. Two proposed models are simulated by computational fluid dynamics (CFD) in two cases of wind velocities. The two models have different both of dimensions at passages and cavities between buildings and shapes of windward sides of buildings. The wide distances between passages of buildings at the same row and rectangular shapes that have slope exterior wall in two directions at the windward sides are devoted to Aswan. The narrow distances between passages of buildings at the same row and rectangular shapes that have trapezoid courtyards that face wind are devoted to Farafra. The results show that the Aswan model can achieve at the inlet surfaces (windward side of buildings) 1.8-2.4 m/s (60-80% of wind velocity) especially at the second and third rows of indoor air velocity which is the required indoor air velocity for comfort. The Farafra model which uses a courtyard can achieve at the inlet surface 1-1.2 m/s (33-41% of wind velocity) which is less than the required indoor air velocity for comfort. The results can achieve the high rate of wind velocity 38-70% and between two and three times comparing favorably with previous studies that report only 20% of wind velocity at the second row and 15% of wind velocity at the third row.     

Power consumption benchmark for a semiconductor cleanroom facility system

Benchmarking is an important step in implementing energy conservation in a semiconductor fabrication plant (hereafter referred to as “fab”). A semiconductor cleanroom facility system is complicated, usually comprised of several sub-systems, such as a chilled water system, a make-up system, an exhaust air system, a compressed air system, a process cooling water (PCW) system, a nitrogen system, a vacuum system, and an ultra-pure water (UPW) system. It is a daunting task to allocate energy consumption and determine an optimum benchmark. This study aims to establish the energy benchmark of a typical 8-in. DRAM semiconductor fab through field measurement data. Results of the measured energy consumption index were: chilled water system (including chiller, chilled water pump and cooling tower): 0.257 kW/kW (=0.9 kW/RT) in summer and 0.245 kW/kW (=0.86 kW/RT) in winter air recirculation air system: 0.00018 kWh/m³ make-up air system: 0.0042 kWh/m³ general exhaust air system: 0.0007 kWh/m³ solvent exhaust air system: 0.0021 kWh/m³ acid exhaust air system: 0.0009 kWh/m³ alkaline exhaust air system: 0.0025 kWh/m³ nitrogen system: 0.2209 kWh/m³ compressed dry air system: 0.2250 kWh/m³ process cooling water system: 1.3535 kWh/m³ and ultra-pure water system: 9.5502 kWh/m³. These data can be used to assess the efficiency of different energy-saving schemes and as a good reference for factory authorities. The PCW system's status before and after implementing energy conservation is discussed.     

Estimating the effect of using cool coatings on energy loads and thermal comfort in residential buildings in various climatic conditions

The impact from using cool roof coatings on the cooling and heating loads and the indoor thermal comfort conditions of residential buildings for various climatic conditions is estimated. The energy cooling loads and peak cooling demands are estimated for different values of roof solar reflectance and roof U-value. The results show that increasing the roof solar reflectance reduces cooling loads by 18–93% and peak cooling demand in air-conditioned buildings by 11–27%. The indoor thermal comfort conditions were improved by decreasing the hours of discomfort by 9–100% and the maximum temperatures in non air-conditioned residential buildings by 1.2–3.3 °C. These reductions were found to be more important for poorly or non-insulated buildings. For the locations studied, the heating penalty (0.2–17 kWh/m² year) was less important than the cooling load reduction (9–48 kWh/m² year). The application of cool roof coatings is an effective, minimal cost and easy to use technique that contributes to the energy efficiency and the thermal comfort of buildings.     

Optimum, technical and energy efficiency design of residential building in Mediterranean region

Jordan heavily relies on imported oil and gas for meeting its energy need as the same time the construction sector consumed more than half of the total electricity consumption in Jordan in 2008. In order to provide the occupants with thermal comfort at least cost, applying energy saving measures into early design stage can be significant to achieve this goal.This paper discusses an assessment of best orientation of the building, windows size, thermal insulation thickness from energetic, economic and environmental point of view for typical residential building located in Mediterranean region. The results show that about 27.59% of annual energy consumption can be saved by choosing best orientation, optimum size of windows and shading device, and optimum insulation thickness. The Life Cycle Cost (LCC) is reduced by 11.94%. The specific energy consumption per square meter is 64 kWh/m² a.     

Analyzing growth and mortality in a subtropical urban forest ecosystem

Information on urban tree growth, mortality and in-growth is currently being used to estimate urban forest structure changes and ecosystem services such as carbon sequestration. This study reports on tree diameter growth and mortality in 65 plots distributed among four land use categories, which were established in 2005/2006 in Gainesville, Florida, USA and were re-measured in 2009. Models for mortality and in-growth models were developed by grouping species into hardwoods and softwoods. Annual change in tree diameter at breast height growth was analyzed using three tree species groups based on potential height and longevity. Additionally, the four most common tree species in the study area were modeled to explore factors affecting tree growth. The average annual mortality rate in the city was 9.97%. Trees located in Institutional land use/land cover (LULC) had the highest annual mortality rate (19.2%/yr), and commercial had the lowest (3.1%/yr). Overall, growth rates for the study area (0.70 cm/yr) and residential LULC (0.80 cm/yr) were comparable to other studies. Growth rates for trees in forested areas were higher (0.56 cm/yr) than those previously reported. Individual species-level growth rates such as those for Juniperus virginiana (1.24 cm/yr) and Quercus virginiana (1.08 cm/yr) were different than other species values reported in other studies. Maintenance activities, site conditions, soil properties, tree characteristics, and LULC significantly influenced urban tree growth, mortality, and in-growth. Results can be used to better understand urban forest ecosystem structure and services in medium sized, subtropical cities and to make better decisions regarding planting and maintenance strategies.     

Eawag Forum Chriesbach—Simulation and measurement of energy performance and comfort in a sustainable office building

The Eawag's new headquarters “Forum Chriesbach” is an exemplary illustration of a ‘sustainable’ construction design for office buildings. With a unique combination of architectural and technical elements the building reaches a very low 88 kWh/m² overall primary energy consumption, which is significantly lower than the Swiss Passive House standard, Minergie-P. A monitoring and evaluation project shows that the building is heated mainly by using the sun and internal heat gains from lighting, electrical appliances and occupants, resulting in an extremely low space heating demand. Cooling is provided by natural night time ventilation and the earth-coupled air intake, which pre-cools supply air and provides free cooling for computer servers. However, values for embodied energy and electricity consumption remain significant, even with partial on-site electricity production using photovoltaics. TRNSYS computer simulations show the contributions of individual building services to the overall energy balance and indicate that the building is resilient towards changes in parameters such as climate or occupancy density. Measurements confirm comfortable room temperatures below 26 °C, even during an extremely hot summer period, and 20-23 °C in the winter season. An economic analysis reveals additional costs of only 5% compared to a conventionally constructed building and a payback-time of 13 years.     

Life cycle energy analysis of buildings: An overview

Buildings demand energy in their life cycle right from its construction to demolition. Studies on the total energy use during the life cycle are desirable to identify phases of largest energy use and to develop strategies for its reduction. In the present paper, a critical review of the life cycle energy analyses of buildings resulting from 73 cases across 13 countries is presented. The study includes both residential and office buildings. Results show that operating (80-90%) and embodied (10-20%) phases of energy use are significant contributors to building's life cycle energy demand. Life cycle energy (primary) requirement of conventional residential buildings falls in the range of 150-400 kWh/m² per year and that of office buildings in the range of 250-550 kWh/m² per year. Building's life cycle energy demand can be reduced by reducing its operating energy significantly through use of passive and active technologies even if it leads to a slight increase in embodied energy. However, an excessive use of passive and active features in a building may be counterproductive. It is observed that low energy buildings perform better than self-sufficient (zero operating energy) buildings in the life cycle context. Since, most of the case studies available in open literature pertain to developed and/or cold countries; hence, energy indicative figures for developing and/or non-cold countries need to be evaluated and compared with the results presented in this paper.     

Heat requirements and energy use in British houses

Housing data likely ranges of insulation levels are combined to give estimates of the heating requirements for conventional houses and small flats to be built in Britain in 1977–1987. After allowance for non-solar heat gains, requirements of 65–120 kWh/day for 4–6 person houses and of 8–47 kWh/day for small flats are predicted. The 65 kWh/day lower limit for houses will be improved on in the case of very well insulated houses using modified construction techniques.Data are collated showing average incidental heat gains from appliances, water heating, and other sources. The effects of these on annual heating energy use and on mean power requirements are assessed, and annual heating energy use per kW of design heat loss is calculated for a range of levels of incidental gains at three British locations; Pembroke, Croydon and Edinburgh. The typical solar contribution to this heating energy is also calculated.Mean-to-peak power variations are considered, showing that on average a heating system operates at 20–30% of the house design heat loss; this is the level at which energy use efficiency is most significant.The theoretical predictions of heating energy use are shown to give reasonable agreement with actual use as measured in field trials, despite the wide variability of the latter. The variation of total solar heating with orientation of a house with windows on two opposite sides is studied in the Appendix, showing a variation of ±15% in winter and ±6% in spring and summer for a particular house design.     

Simplified method of sizing and life cycle cost assessment of building integrated photovoltaic system

This paper presents methodology to evaluate size and cost of PV power system components. The simplified mathematical expressions are given for sizing of PV system components. The PV array size is determined based on daily electrical load (kWh/day) and number of sunshine hours on optimally tilted surface specific to the country. Based on life cycle cost (LCC) analysis, capital cost (US$/kW_P) and unit cost of electricity (US$/kWh) were determined for PV systems such as stand-alone PV (SAPV) and building integrated PV (BIPV). The mitigation of CO₂ emission, carbon credit and energy payback time (EPBT) of PV system are presented in this paper. Effect of carbon credit on the economics of PV system showed reduction in unit cost of electricity by 17-19% and 21-25% for SAPV and BIPV systems, respectively. This methodology was illustrated using actual case study on 2.32 kW_P PV system located in New Delhi (India).     

Energy-efficient terrace houses in Sweden: Simulations and measurements

Reducing energy use in buildings is essential to decrease the environmental impact. Outside Gothenburg in Sweden, 20 terrace houses were built according to the passive house standard and completed in 2001. The goal was to show that it is possible to build passive houses in a Scandinavian climate with very low energy use and to normal costs. The houses are the result of a project including research, design, construction, monitoring and evaluation. The passive house standard means that the space heating peak load should not exceed 10 W/m² living area in order to use supply air heating. This requires low transmission and ventilation losses and the building envelope is therefore highly insulated and very airtight. A mechanical ventilation system with approximately 80% heat recovery is used. The electric resistance heating in the supply air is 900 W per living unit. Solar collectors on the roof provide 40% of the energy needed for the domestic hot water. The monitored delivered energy demand is 68 kWh/m² a. Energy simulations show that main differences between predicted and monitored energy performance concern the household electricity and the space heating demand. Total delivered energy is approximately 40% compared with normal standard in Sweden.     

Energy consumption and ventilation performance of a naturally ventilated ecological house in a cold climate

In this paper, the thermal and ventilation performance of an ecological house in Helsinki, Finland are presented. The single-family dwelling has a well-insulated, wooden frame construction with no plastic vapour retarder. The measured and simulated results show that the energy consumption of the house is low and that the outdoor ventilation rate is generally satisfactory based on the measured CO₂ concentrations. Extrapolating the measured ventilation data shows that, when the operable windows are closed, the ventilation rate is expected to be about 0.45 air-changes-per-hour (ach) in the winter and about 0.25 ach in the summer. The consumption of total primary energy and space heating energy were measured to be 30% less (162 kWh/(m² a)) and 36% less (76 kWh/(m² a)) than in typical Finnish houses, respectively. The paper also uses a numerical model to investigate the sensitivity of energy consumption to the insulation level, household electricity and domestic hot water consumption, window area, ventilation rate and heat recovery effectiveness.     

A comparison of pilot-scale photocatalysis and enhanced coagulation for disinfection byproduct mitigation

This study evaluated pilot-scale photocatalysis and enhanced coagulation for their ability to remove or destroy disinfection byproduct (DBP) precursors, trihalomethane (THM) formation potential (FP), and THMs in two Arizona surface waters. Limited photocatalysis (<5 kWh/m³) achieved reductions in most of the DBP precursor parameters (e.g., DOC, UV₂₅₄, and bromide) but led to increased chlorine demand and THMFP. In contrast, enhanced coagulation achieved reductions in the DBP precursors and THMFP. Extended photocatalysis (<320 kWh/m³) decreased THMFP once the energy consumption exceeded 20 kWh/m³. The photocatalytic energy requirements for THM destruction were considerably lower (EEO = 20-60 kWh/m³) than when focusing on precursor destruction and THMFP. However, rechlorination increased the total THM (TTHM) concentration well beyond the raw value, thereby negating the energy benefits of this application. Enhanced coagulation achieved consistent 20-30% removals of preformed THMs. Outstanding issues need to be addressed before TiO₂ photocatalysis is considered feasible for DBP mitigation; traditional strategies, including enhanced coagulation, may be more appropriate.