The prospects for solar energy use in industry within the United Kingdom

An assessment of the potential for solar energy applications within U.K. industry has been made, using a disaggregated breakdown of energy consumption in the eight industrial sectors by fuel and end-use, and taking account of solar collector performance under U.K. climatic conditions. Solar contributions of 35 per cent of process boiler heat up to a temperature of 80°C and 10 per cent in the 80–120°C range are considered feasible, along with 35 per cent of non-industrial water heating. After employing energy conservation techniques currently more cost-effective than solar systems, an additional 3.5 per cent of U.K. primary energy expended in manufacturing industry (excluding iron and steel production) could be contributed by solar. This represents 1 per cent of the U.K. national primary energy demand. Improvements in collector efficiency, less costly interseasonal energy storage systems, and the changing pattern of U.K. industry could increase this percentage considerably.     

Technical and economic performance of residential solar water heating in the United States

This paper examines the regional, technical, and economic performance of residential rooftop solar water heating (SWH) technology in the U.S. It focuses on the application of SWH to consumers in the U.S. currently using electricity for water heating, which currently uses over 120 billion kWh per year. The variation in electrical energy savings due to water heating use, inlet water temperature and solar resource is estimated and applied to determine the regional “break-even” cost of SWH where the life-cycle cost of SWH is equal the life-cycle energy savings. For a typical residential consumer, a SWH system will reduce water heating energy demand by 50–85%, or a savings of 1600–2600 kWh per year. For the largest 1000 electric utilities serving residential customers in the United States as of 2008, this corresponds to an annual electric bill savings range of about $100 to over $300, reflecting the large range in residential electricity prices. This range in electricity prices, along with a variety of incentives programs corresponds to a break-even cost of SWH in the United States varying by more than a factor of five (from less than $2250/system to over $10,000/system excluding Hawaii and Alaska), despite a much smaller variation in the amount of energy saved by the systems (a factor of approximately one and a half). We also consider the relationships between collector area and technical performance, SWH price and solar fraction (percent of daily energy requirements supplied by the SWH system) and examine the key drivers behind break-even costs.     

Net benefits of energy conservation in housing

The computer program FREDOCAN allows one to assess the impact of energy conservation policies on the household sector due to thermal insulation measures and to various options concerning domestic heating plants. the insulation policy must be specified, giving in input to the program the housing stock and the fraction of dwellings to be insulated as a function of time. the different insulation measures are evaluated both separately and in a combined way. the evaluations are performed both from financial and energy analysis point of view, determining the internal rates of return of the investments, financial and energy pay-back times under static and dynamic conditions. The space heat savings evaluated in the first part of the program allow one to calculate, in the second part, additional savings due to the reduction of the investments required for the heating plants. It is also possible to assess the variation with time of the heating plant mix, taking into account of improved efficiencies and different energy sources. A test case for the North of Italy is described. It shows that a very simple insulation of both existing and new houses limits the growth of energy demand to only 18 per cent above the 1977 consumption levels, although the combined effects of new constructions and of an extensive upgrading of heating systems would require a 75 per cent energy demand increase.     

Identifying key design parameters of the integrated energy system for a residential Zero Emission Building in Norway

This study examined an integrated solution of the building energy supply system consisting of flat plate solar thermal collectors in combination with a ground-source heat pump and an exhaust air heat pump for the heating and cooling, and production of domestic hot water. The supply energy system was proposed to a 202 m² single-family demo dwelling (SFD), which is defined by the Norwegian Zero Emission Building standard. The main design parameters were analyzed in order to find the most essential parameters, which could significantly influenced the total energy use. This study found that 85% of the total heating demand of the SFD was covered by renewable energy. The results showed that the solar energy generated by the system could cover 85–92% and 12–70% of the domestic hot water demand in summer and winter respectively. In addition, the solar energy may cover 2.5–100% of the space heating demand. The results showed that the supply air volume, supply air and zone set point temperatures, auxiliary electrical volume, volume of the DHW tank, orientation and tilt angle and the collector area could influenced mostly the total energy use.     

The potential for electricity conservation and peak load reduction in the residential sector of Brazil

This paper summarizes the methodological approach and the results of a study aimed at assessing the potential for electricity conservation and peak load reduction in the Brazilian residential sector. The study splits the residential sector into 15 subsectors, considering five different geographical regions and three household income classes. Technical, economic and market potentials are determined both for electrical energy conservation and peak load reduction in the period from 2000 to 2020. The main findings show an electricity conservation technical potential for the residential sector of 28%, an economic potential of 14% and market potentials of 12% and 8%. The corresponding results found for the peak load reduction in 2020 were a technical potential of 21%, an economic potential of 4% and market potentials of 3% and 2%, with the large reduction in percentage savings for peak demand in the economic and market scenarios explained in particular by the omission of solar water heating from those scenarios. Finally, carbon dioxide emission reductions associated with the electricity conservation potentials and peak load reductions are also estimated.     

The use of floor panel energy storage in a heat pump heated dwelling

A method of improving the performance of heat pumps for domestic space heating has been investigated. The study focuses on the short-term storage of heat pump output energy in concrete floor panels. This paper describes the dynamic computer simulation of an air to water heat pump, a floor panel energy store and energy flowpaths in a dwelling. The heating plant, controls and building thermal behaviour, were simulated as a complete energy system to enable the study of interactions between the subsystems. The model heating system comprised a number of under floor water heated panels installed in ground floor rooms of a two storey dwelling. Supplementary energy was supplied by direct electric heaters situated in most rooms. Heat pump operating periods were controlled as a function of the external air temperature within two prescribed occupancy intervals per day. Results of the investigation indicate that a heat pump system using floor panel storage and emission may be efficiently managed to provide nearly continuous heating with little supplementary energy input. The short-term storage of energy in thick floor panels allowed the heat pump to be operated for extended periods without cycling. Because of this, the seasonal loss in heat pump performance resulting from intermittent operation was less than 1 per cent. Attempting to supply the total space heating load with the heat pump and floor panel system resulted in severe overheating during periods of high solar or casual gain. Under these conditions the simple control strategy based on the measurement of external air temperature was ineffective. This problem was eliminated by reducing the heat pump energy input to the dwelling and supplying about 10 per cent of the seasonal energy demand by direct electric heaters. The influence of floor panel energy storage capacity on the performance of the heating system was investigated. Concrete panel depths of between 25 and 150 mm were considered. The seasonal system efficiency was found to increase with floor panel thickness, although not significantly with panel depths beyond 100 mm. The extensive use of floor slabs to store energy caused mean floor temperatures to be higher than when using direct electric air heaters only. However, with the depth of under floor insulation considered in the study (75 mm), heating the floor slab increased the seasonal energy loss of the building by only 4 per cent.     

科学用能与分布式能源系统

从对能源的中长期需求和能源供应能力的缺口出发,论证了节能和科学用能应当是我国能源发展战略的核心。阐述了科学用能的研究内容、方法和主要特点,指出应重点抓住高耗能产业和科学用能的共性科技问题。对建筑科学节能,提出尽可能采用可再生能源和环境能源以节约化石能源和电能。分布式能源系统是科学用能的范例,它与集中式发电的有机结合是新世纪电力工业和能源工业的重要发展方向。开发小型和微型燃气轮机可以提升我国动力工业的技术水平;正确确定冷热电三者的关系,充分发挥中低温余热的作用,是使分布式能源系统获得最大节能效果和最大经济效益的关键。     

On cost‐effective technical measures to avoid environmental damages of regional energy systems

The production of heat and electricity can cause large environmental impacts and, hence, large costs for society. Those are costs that are seldom taken into consideration. An important question is how the future technical energy systems should be formed if environmental costs were considered as any other good or service, such as raw material, capital and labour. This study comprises cost‐effective technical measures when monetary values of external effects are included in an energy system analysis. It is an analysis of how the present energy system can for society be cost‐effectively reconstructed to be more sustainable. A regional energy system model has been developed to perform the study and it concentrates upon production of heat in single‐family houses, multi‐dwelling buildings, non‐residential premises and district heating systems. The analysis adopts a business economic perspective, using present prices of energy carriers, and a more socio‐economic perspective, in which external costs are included. The result of the analysis is the optimal mix of energy carriers as well as new and existing heating plants that minimizes the costs of satisfying a demand for heat. The results show that it is profitable to invest in new heating plants fuelled with woody biomass. Furthermore, the external costs arising with satisfying the demand for heat can decrease substantially, 60%, by carrying through with the investments that are cost‐effective according to the institutional rules valid today. When monetary values of external costs are taken into consideration, this number is additional 5‐percentage points lower. It is shown that if environmental costs are included it is more expensive to continue with business as usual than it is to reconstruct and run a more sustainable energy system. Copyright © 2002 John Wiley & Sons, Ltd.     

Solid oxide fuel cell micro combined heat and power system operating strategy: Options for provision of residential space and water heating

Solid oxide fuel cell (SOFC) based micro combined heat and power (micro-CHP) systems exhibit fundamentally different characteristics from other common micro-CHP technologies. Of particular relevance to this article is that they have a low heat-to-power ratio and may benefit from avoidance of thermal cycling. Existing patterns of residential heat demand in the UK, often characterised by morning and evening heating periods, do not necessarily complement the characteristics of SOFC based micro-CHP in an economic and technical sense because of difficulties in responding to large rapid heat demands (low heat-to-power ratio) and preference for continuous operation (avoidance of thermal cycling). In order to investigate modes of heat delivery that complement SOFC based micro-CHP a number of different heat demand profiles for a typical UK residential dwelling are considered along with a detailed model of SOFC based micro-CHP technical characteristics. Economic and environmental outcomes are modelled for each heat demand profile. A thermal energy store is then added to the analysis and comment is made on changes in economic and environmental parameters, and on the constraints of this option. We find that SOFC-based micro-CHP is best suited to slow space heating demands, where the heating system is on constantly during virtually all of the winter period. Thermal energy storage is less useful where heat demands are slow, but is better suited to cases where decoupling of heat demand and heat supply can result in efficiencies.     

Thermal behaviour of an eighteenth-century Athenian dwelling

Two forms of traditional dwelling were identified during a study tour of Greece. A representative Athenian dwelling from the Plaka district, next to the Acropolis, was selected for study using the TAS° thermal analysis software. The predictions from the computer simulations indicated that, if the building considered was used either as originally intended or when adapted for modern living, comfortable internal conditions would ensue during both the summer and winter seasons. The south-facing hayati (i.e. the upper-floor-level entrance verandah) was fitted with removable glazing. This feature had a beneficial effect on the temperatures for the adjoining rooms during the summer and winter seasons. The improved summertime performance may, in part, explain the frequent occurrence of this usually unglazed passive-solar feature in the vernacular domestic architecture of mainland Greece. The behaviour of a well thermally insulated version of the dwelling was also modelled. Whilst such a dwelling was more energy efficient, having significantly reduced energy loads for the space heating required at the present time, a tendency was detected for part of the upper floor accommodation of the insulated building to overheat during the summer months. This suggests that there is a need to evaluate, and consider carefully, the thermal behaviour during both summer and winter when contemplating the refurbishment of such historic dwellings for conservation purposes and compliance with the thermal thrift requirements of the proposed building regulations.     

推动长江经济带冬季清洁取暖 满足人民美好生活需要

推进长江经济带绿色发展是国家的重大战略。长江经济带沿线9省2市聚焦了全国42%的人口,长期以来冬季室内温度普遍较低、热舒适性较差,居民要求冬季取暖的呼声日渐强烈,未来取暖用能增长强劲。推动长江经济带冬季清洁取暖是满足人民美好生活需要的具体体现,但是目前还存在认识不一致、技术路径不清晰、房屋保温性能差、影响区域能源供需平衡等问题。建议国家按照“生活品质提升”的定位,坚持政府引导、市场主导原则推进长江经济带夏热冬冷地区冬季清洁取暖工作,加强技术指导和建筑节能标准的落实,统筹长江经济带能源协同发展,提高取暖用能保障能力。     

China's energy consumption under the global economic crisis: Decomposition and sectoral analysis

It is now widely recognized that there is a strong relationship between energy consumption and economic growth. Most countries′ energy demands declined during the economic depression of 2008–2009 when a worldwide economic crisis occurred. As an export-oriented economy, China suffered a serious exports decline in the course of the crisis. However, it was found that energy consumption continued to increase. Against such a background, this paper aims to assess and explain the factors causing the growth of energy consumption in China. First, we will explain the impact of domestic final use and international trade on energy consumption by using decomposition analysis. Second, embodied energy and its variation across sectors are quantified to identify the key sectors contributing to the growth. Lastly, the policy implications for long-term energy conservation are discussed. The results show that the decline in exports was one of the driving forces for energy consumption reduction in the crisis, but that the growth of domestic demand in manufacturing and construction, largely stimulated by economic stimulus plans, had the opposite effect on energy consumption. International trade contributed to decreasing energy consumption of China during and after the crisis because the structure of exports and imports changed in this period.     

Variability of energy use for domestic space heating

The level of reported variability of domestic space heating energy use is extremely high, the coefficient of variation being 20% even for groups of similar houses. In consequence, there is a need for heating systems to work effectively and economically over a wide range of energy use levels and there is also a need for large sample sizes in evaluating field results if the effects of individual factors contributing to the overall variability are to be assessed. For dissimilar houses, samples of 25 or more are necessary for the detection of individual factors and hundreds may be required for their accurate estimation.The effect on energy use of night temperature set-back is shown theoretically to be equivalent to a 2$\text{1}\text{2}$% energy saving per degree Kelvin temperature depression. The effects of more intermittent heating system operation are provisionally estimated, a 50% energy saving being estimated for a 6-h period of daily use at the required temperature. Effects of choice of internal temperature and ventilation rate on energy use are assessed.The energy savings made by such personal control strategies can be nullified by equipment deficiencies. The magnitudes of the effects of three such deficiencies (pipe or duct losses, unresponsive emitter control and upstairs overheating in mild weather) are estimated as each adding around 20% to the heating energy use of a typical house.The combined effects of energy saving strategies and equipment deficiencies make possible annual energy use figures from half to one-and-a-half times the designed level. The implications of this variability for heating system design are discussed.     

Residential space heating: An analysis of energy conservation

The energy signature technique is used to analyse the marginal benefits of various types of energy conservation in residential space heating and certain systematic errors frequently committed by utility companies in estimating these benefits. The results indicate that the marginal price of energy and the change in the balance point temperature of a dwelling are the most significant factors in determining the value of energy saved each year. Utilities in the 27 cities studied do not consider the effects of changes in the balance point temperature of a structure when estimating energy savings. Regional differences are also examined.     

Third World energy policies Demand management and conservation

Increasing energy costs underline the need for more efficient management of energy supply and demand to maintain economic growth, especially in the resource scarce developing countries. Combining policy tools for demand management and conservation (including pricing, physical controls, technical methods, and education) yields the best results. Pricing policy takes into account the efficiency costs of energy supply required to meet economic objectives. This is then adjusted to satisfy other objectives of pricing such as social-subsidy considerations, financial viability, conservation, price stability, etc. Energy conservation programmes should be implemented only after determining whether their economic benefits exceed the corresponding costs.     

A systematic techno-economic assessment of a WEC system installation for low-cost electrification of a habitable dwelling

This paper deals with the technical feasibility and economic viability of a grid connected wind-energy conversion system (WECS) used to cover the energy demand of an average habitable dwelling. The various parts of the wind-energy system are described and the useful electrical energy production is determined using a simulation program based on the Monte Carlo method. An economic analysis of the WEC system is performed using a computerized assessment tool. Important financial indices are calculated and financial scenarios investigated.     

Solar heating system performance estimation using sinusoidal inputs

A method is presented for the estimation of the fraction of the heating load supplied by solar energy during the heating season. This procedure remains useful even when system design parameters are far from the norm, and in particular is applicable to systems incorporating seasonal storage of heat. Insolation, temperature and hot water demand are input as sinusoids, and the closed-form solution of the heat transfer differential equation is found. The method as presented here is suitable for domestic hot water and liquid space heating systems.     

District cooling and heating with seawater as heat source and sink in Dalian, China

This paper presents a study on the utilization of ocean thermal energy in Dalian. Coastal areas are ideal sites for the application of seawater-source heat pump technology (SWHP) to provide district cooling and heating. The technical requirements and the scheme design in the context of marine climate are discussed. A government-commissioned feasibility study of a proposed district energy site in Dalian, with an estimated 68 MW heating load and 76 MW cooling load plant capacity is then described. The economic, energy and environmental impacts are analyzed. In order to get a better understanding of economic justification and benefits of two different systems, annual cost (AC) and net present value (NPV), are used. A series of sensitivity analyses are undertaken to investigate the magnitude of the effect of the parameters variation on cost calculation. The numerical simulations of seawater temperature field are performed by using a two-dimensional convection–diffusion equation model to evaluate environmental impacts. Study indicates that Dalian has great potential for applying SWHP system. It is both technically and economically feasible because of the favorable geographical location and urban environment.     

Cost-benefit analysis of domestic energy efficiency

There are a number of driving forces behind energy efficiency. In recent times, the Kyoto Protocol has been the most prominent in bringing energy efficiency to the fore. In some countries, the domestic sector has been highlighted as an area which has a significant potential for improvement. However, prior to the implementation of large-scale energy-efficiency programmes, it is important to evaluate whether they make economic sense. Heretofore, most economic evaluations of energy-efficiency programmes have concentrated purely on the associated costs of the programmes and the energy savings that result. At best, reductions in environmental benefits are also estimated, but rarely are other benefits calculated, such as increases in the levels of household comfort and improvements in human health. This paper endeavours to provide a template for ex ante economic evaluations of domestic energy-efficiency programmes. A comprehensive cost–benefit analysis of a programme to retrofit various energy-efficiency technologies and heating upgrades to the Irish dwelling stock is taken as a case study. The study demonstrates how energy savings, environmental benefits, and health and comfort improvements may be assessed. In so doing, it provides insights into the methodological difficulties and solutions for assessing the social efficiency of large-scale domestic energy-conservation projects.     

Energy consumption of residential buildings and occupancy profiles. A case study in Mediterranean climatic conditions

Residential energy consumptions are determined by the interaction of many factors. Apart from physical characteristics such as climate, heating type, age, and size of the house, occupants’ behavior and socio-economic aspects are critical. Furthermore, the relative impact of the occupants’ characteristics and behavior seems to differ in various investigations confirming the importance of contextual analysis. In this study, different procedures for obtaining occupancy profiles are described and applied with reference to a residential building stock located in Mediterranean climatic conditions (Italy). The heating and domestic hot water (DHW) energy consumptions and indoor comfort conditions of a representative building were determined by introducing different occupant scenarios in dynamic simulations. The occupancy profiles were built by means of data collected at the University of Calabria using surveys, interviews, bills, and statistical elaborations. Considering different modes of use of the dwelling (Regulations, Current-use, and Statistical), in the simulation process, all the inputs of occupancy, ventilation, lighting, DHW, and heating operation were modified. The Regulations occupancy profile produces an underestimation of heating energy consumption. Additionally, primary energy for DHW is strongly affected by the family composition. The effect of the occupants’ preferences on the energy performance of the building was investigated: mainly energy consumptions and internal comfort conditions vary with the set point temperature and the duration of ventilation. The analysis provides reference procedures for obtaining occupancy profiles. Furthermore, the simulation results demonstrate the significant dependence of heating and DWH primary energy consumption on the characteristics and preferences of occupants in the Mediterranean climate.