Energy, economic and environmental analysis on RET-hydrogen systems in residential buildings

The aim of this study was to analyze energy, economic and environmental performances of a set of scenarios dealing with the production and the use of hydrogen as energy carriers in residential applications in combination with renewable energy (RE).The authors also made an investigation into the required economic conditions necessary for making H₂–RE residential systems competitive with conventional ones, which are based on the use of grid electricity and natural gas.A case study was enacted in a small residential district in Palermo (Italy) made by five multi-storey buildings.Many energy systems have been considered according to several fuel-device combinations (electric grid, fuel cell, PV panels, wind turbines, boiler etc.).The software HOMER (hybrid optimization model for electric renewables), developed by NREL and Midwest Research Institute (USA), was used, in order to study the energy balance of the system and its components. Moreover, it was possible to simulate the hourly operation of each system and to calculate technical, economic and environmental performance parameters.The net present cost and the cost of energy are the two main parameters used to compare economic performances of the systems with both actual and expected costs in the medium term.A sensitivity analysis was carried out in order to appreciate the most important parameters influencing the economic performances of the systems and to define possible future scenarios of competitiveness between technologies.Emissions of CO₂ (the most important greenhouse gas) and other pollutants have been considered for an environmental benefits analysis.     

Energy and cost analysis of semi-transparent photovoltaic in office buildings

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.     

Multi-farm economic analysis of perennial energy crops in Central Greece, taking into account the CAP reform

This study analyses farm level economic impacts of biomass production from perennial crops including Arundo donax L. (arundo), Miscanthus x giganteus (miscanthus), Panicum virgatum L. (switchgrass) and Cynara cardunculus L. (cardoon). Regional biomass supply curves are estimated with a dynamic, multi-farm, mathematical programming model. Micro-economic data for the model are generated from farm surveys covering 52 farms containing a total of 400 parcels, in Central Greece. The study also examines the potential effects of the Common Agricultural Policy reform in 2003 on regional biomass supply. Simulations show that the policy reform toward decoupled subsidies lowers the cost of biomass between 15 and 25 euro per tonne. Switchgrass appears to be the most attractive option, followed by cardoon and miscanthus. Due to high specific machinery cost, arundo is never preferred. Relative to the agricultural policy setting of Agenda 2000, the biomass potential increases more for farms of small economic size and farms with a higher share of cotton.     

Multi-criteria decision analysis and cost–benefit analysis of alternative scenarios for the power generation sector in Greece

This paper examines four mutually exclusive scenarios for the expansion of the Greek electricity system developed by official authorities and representing alternative views on meeting electricity demand. The aim is to encompass all positive and negative side-effects characterizing the electricity generation technologies assumed to participate in each scenario and emphasis is given to the particular role of renewable energy sources which represent a major differentiating factor between them. The calculation of economic, technical and environmental performances of the examined scenarios for the year 2010 shows that electricity planning is a complicated task since improvements in one policy target are accompanied by losses in others. In order to resolve this conflict, the scenarios are comparatively evaluated with two decision support techniques, multicriteria decision analysis and cost–benefit analysis, which are capable of broadening the strict boundaries of a financial analysis while avoiding intuitive solutions that are often applied in practice. Following the two completely different evaluation approaches, it is confirmed that the scenario assuming the highest penetration of renewable energy sources is the best compromise configuration for the Greek power generation sector.     

固体吸附除湿技术用于民用建筑中央空调系统的经济性分析

针对传统空调冷却除湿方式的高能耗,提出将固体吸附除湿技术应用于民用建筑中央空调系统,并对采用这种除湿方式的干式风机盘管加固体吸附独立除湿新风系统与传统的风机盘管加新风系统在运行能耗方面进行经济性实例分析,结果表明干式风机盘管加固体吸附独立除湿新风系统较传统风机盘管加新风系统其夏季空调工况每天减少约14W/m2,有效降低建筑能耗。     

The cost benefit analysis and potential emission reduction evaluation of applying wall insulation for buildings in Malaysia

Due to the rapidly increasing number of air-conditioned spaces in buildings, the electricity demand has significantly increased during the past decade in Malaysia. The present energy analysis attempts to predict the long term environmental impact of utilizing thermal insulation materials for exterior walls of Malaysian buildings. The optimum insulation thickness is mainly influenced by local electricity tariff rate, and the capital insulation outlays. In the present work, some of the commonly used insulators available in the Malaysian market were analyzed. The results show that 2.2 cm of fibreglass–urethane produces the largest cost savings, of around 1.863US$/m² and is the most economically feasible insulation material that reduces the annual CO₂ emission production level by 16.4 kg/m². The main focus of the survey is to predict the potential emission production fluctuation for over the next 20 years. In this regard, three different scenarios were introduced, based on different electricity production policies. It was revealed that the increase in the contribution of renewable power plants on one hand, and phasing out of the conventional thermal coal plants on the other will substantially lead to a diminished CO₂ emission in long term.     

Environmental and economic cost analysis of housing in temperate climate using an innovative lightweight partitioning system

This paper presents an economic and environmental cost analysis of a representative Portuguese housing dwelling unit using an innovative lightweight adjustable membrane partitioning system, developed within a research project. The environmental and economic costs of this system, both on the construction and occupancy phases, were compared with the Portuguese conventional dividing wall solution, in hollow brick, simulated on the same reference dwelling, using the same layout and remaining constructive elements. The occupancy phase costs were evaluated by computer simulation, which allowed determining how the occupancy schedule of daytime and night time occupied areas may influence the cooling and heating needs for different solar orientations.     

Techno-economic analysis of fuel conversion and power generation systems — the development of a portable chemical process simulator with capital cost and economic performance analysis capabilities

The development is described of ECLIPSE, a suite of programs written in C for IBM PC compatible computers, which permits the full technical and economic analysis of current and proposed fuel conversion and power generation systems. A large advantage is the flexibility of approach which is possible and the degree of integration of the technical and economic aspects of the problem. The package includes extensive chemical properties, utilities and capital costing databases which can be modified by the user.     

Economic analysis of hydrogen production through a bio-ethanol steam reforming process: Sensitivity analyses and cost estimations

In this study, the hydrogen selling price from ethanol steam reforming has been estimated for two different production scenarios in the United States, i.e. central production (150,000 kg H₂/day) and distributed (forecourt) production (1500 kg H₂/day), based on a process flowchart generated by Aspen Plus^® including downstream purification steps and economic analysis model template published by the U.S Department of Energy (DOE) [1]. The effect of several processing parameters as well as catalyst properties on the hydrogen selling price has been evaluated. $2.69/kg is estimated as the selling price for a central production process of 150,000 kg H₂/day and $4.27/kg for a distributed hydrogen production process at a scale of 1500 kg H₂/day. Among the parameters investigated through sensitivity analyses, ethanol feedstock cost, catalyst cost, and catalytic performance are found to play a significant role on determining the final hydrogen selling price.     

Numerical simulation of cooling energy consumption in connection with thermostat operation mode and comfort requirements for the Athens buildings

A model and a corresponding numerical procedure, based on the finite-difference method, have been developed for the prediction of buildings thermal behavior under the influence of all possible thermal loads and the “guidance” of cooling control system in conjunction with thermal comfort requirements. Using the developed procedure analyses have been conducted concerning the effects of thermostat operation mode and cooling power in terms of the time, on the total cooling energy consumption for the ideal space cooling, as well as for various usually encountered real cases, thus trying to find ways to reduce cooling energy consumption. The results lead to suggestions for energy savings up to 10%. Extensive comparisons between the ideal and various real cooling modes showed small differences in the 24-h cooling energy consumption. Because of the above finding, our detailed ideal cooling mode predictions gain considerable value and can be considered as a basis for comparison with real cases. They may also provide a good estimate of energy savings obtained if we decide to increase thermostat set point temperature. Therefore, as the extent of cooling energy saving is a priori known, one can decide if (and how much) it is worthy to increase thermostat set point temperature at the expense of thermal comfort. All results of the study, which refer to the Typical Athens Buildings during the typical Athens summer day, under the usual ranges of thermal loads, may be applicable to other regions with similar conditions.     

Impact of the ambient temperature rise on the energy consumption for heating and cooling in residential buildings of Greece

Annual values of heating and cooling degree-days for two typical base temperatures, namely 15 °C for heating and 24 °C for cooling, and for the two main cities of Greece (Athens and Thessaloniki) from 1983 to 2002 are presented in the study, calculated using hourly dry bulb temperature records from the meteorological stations of the National Observatory of Athens and of the Aristotle University of Thessaloniki. The decade average (1983–1992 and 1993–2002) values of the heating and cooling degree-days of the two cities are compared, for various base temperatures. The results show that the average value of heating degree-days of Athens for the decade 1993–2002, depending on the base temperature, is reduced from 8% to 22% as compared to the corresponding value of the decade 1983–1992. Similarly, the reduction in the Thessaloniki case is found in the range 4.5%–9.5%. The difference in the average value of cooling degree-days of the decades is more pronounced, the increase ranging from 25% to 69% for Athens and from 10% to 21% for Thessaloniki. In order to evaluate the effect of these changes on the energy requirements for heating and cooling of a typical residential building, the latter were calculated using the variable base degree-day method and the data sets of the two decades. The results show a reduction of the heating energy demand by 11.5% and 5% and an increase of the cooling energy demand by 26% and 10%, for Athens and Thessaloniki respectively.     

Potential benefits of cool roofs on commercial buildings: conserving energy, saving money, and reducing emission of greenhouse gases and air pollutants

Cool roofs—roofs that stay cool in the sun by minimizing solar absorption and maximizing thermal emission—lessen the flow of heat from the roof into the building, reducing the need for space cooling energy in conditioned buildings. Cool roofs may also increase the need for heating energy in cold climates. For a commercial building, the decrease in annual cooling load is typically much greater than the increase in annual heating load. This study combines building energy simulations, local energy prices, local electricity emission factors, and local estimates of building density to characterize local, state average, and national average cooling energy savings, heating energy penalties, energy cost savings, and emission reductions per unit conditioned roof area. The annual heating and cooling energy uses of four commercial building prototypes—new office (1980+), old office (pre-1980), new retail (1980+), and old retail (pre-1980)—were simulated in 236 US cities. Substituting a weathered cool white roof (solar reflectance 0.55) for a weathered conventional gray roof (solar reflectance 0.20) yielded annually a cooling energy saving per unit conditioned roof area ranging from 3.30 kWh/m² in Alaska to 7.69 kWh/m² in Arizona (5.02 kWh/m² nationwide); a heating energy penalty ranging from 0.003 therm/m² in Hawaii to 0.14 therm/m² in Wyoming (0.065 therm/m² nationwide); and an energy cost saving ranging from 0.126/m < sup > 2 < /sup > in West Virginia to0.126/m² in West Virginia to 1.14/m² in Arizona ($0.356/m² nationwide). It also offered annually a CO₂ reduction ranging from 1.07 kg/m² in Alaska to 4.97 kg/m² in Hawaii (3.02 kg/m² nationwide); an NO_x reduction ranging from 1.70 g/m² in New York to 11.7 g/m² in Hawaii (4.81 g/m² nationwide); an SO₂ reduction ranging from 1.79 g/m² in California to 26.1 g/m² in Alabama (12.4 g/m² nationwide); and an Hg reduction ranging from 1.08 μg/m² in Alaska to 105 μg/m² in Alabama (61.2 μg/m² nationwide). Retrofitting 80% of the 2.58 billion square meters of commercial building conditioned roof area in the USA would yield an annual cooling energy saving of 10.4 TWh; an annual heating energy penalty of 133 million therms; and an annual energy cost saving of $0.356/m² nationwide). It also offered annually a CO₂ reduction ranging from 1.07 kg/m² in Alaska to 4.97 kg/m² in Hawaii (3.02 kg/m² nationwide); an NO_x reduction ranging from 1.70 g/m² in New York to 11.7 g/m² in Hawaii (4.81 g/m² nationwide); an SO₂ reduction ranging from 1.79 g/m² in California to 26.1 g/m² in Alabama (12.4 g/m² nationwide); and an Hg reduction ranging from 1.08 μg/m² in Alaska to 105 μg/m² in Alabama (61.2 μg/m² nationwide). Retrofitting 80% of the 2.58 billion square meters of commercial building conditioned roof area in the USA would yield an annual cooling energy saving of 10.4 TWh; an annual heating energy penalty of 133 million therms; and an annual energy cost saving of 735 million. It would also offer an annual CO₂ reduction of 6.23 Mt, offsetting the annual CO₂ emissions of 1.20 million typical cars or 25.4 typical peak power plants; an annual NO_x reduction of 9.93 kt, offsetting the annual NO_x emissions of 0.57 million cars or 65.7 peak power plants; an annual SO₂ reduction of 25.6 kt, offsetting the annual SO₂ emissions of 815 peak power plants; and an annual Hg reduction of 126 kg.     

Manure's allure: Variation of the financial, environmental, and economic benefits from combined heat and power systems integrated with anaerobic digesters at hog farms across geographic and economic regions

Several studies have shown that anaerobic digesters integrated with combined heat and power systems (CHP/AD) are a financially attractive way to generate electricity, reduce odor, and improve nutrient management on hog farms; yet only very few systems have been installed to date. Employing published financial, economic, and environmental indicators, this study tests whether the benefits from CHP/AD identified in these studies can be replicated across all major hog-farming regions in the US. The study finds that a modest support of 1 cent per kWh is needed to assure that CHP/AD generated electricity is competitive with current utility rates in many hog-farming states. However, the study also shows that once CHP/AD systems are promoted hog-farming states stand to reap large benefits from CHP/AD, particularly environmental benefits (such as odor control and emissions reductions), economic benefits (in form of job creation), and added generating capacity.     

Thermal analysis and performance optimization of a solar hot water plant with economic evaluation

The main objective of this study is to optimize the long-term performance of an existing active-indirect solar hot water plant (SHWP), which supplies hot water at 65 °C for use in a flight kitchen, using a micro genetic algorithm in conjunction with a relatively detailed model of each component in the plant and solar radiation model based on the measured data. The performance of SHWP at Changi International Airport Services (CIASs), Singapore, is studied for better payback period using the monthly average hourly diffuse and beam radiations and ambient temperature data. The data input for solar radiation model is obtained from the Singapore Meteorological Service (SMS), and these data have been compared with long-term average data of NASA (surface meteorology and solar energy or SSE). The comparison shows a good agreement between the predicted and measured hourly-averaged, horizontal global radiation.The SHWP at CIAS, which comprises 1200 m² of evacuated-tube collectors, 50 m³ water storage tanks and a gas-fired auxiliary boiler, is first analyzed using a baseline configuration, i.e., (i) the local solar insolation input, (ii) a coolant flow rate through the headers of collector based on ASHRAE standards, (iii) a thermal load demand pattern amounting to 100 m³/day, and (iv) the augmentation of water temperature by auxiliary when the supply temperature from solar tank drops below the set point. A comparison between the baseline configuration and the measured performance of CIAS plant gives reasonably good validation of the simulation code. Optimization is further carried out for the following parameters, namely; (i) total collector area of the plant, (ii) storage volume, and (iii) three daily thermal demands. These studies are performed for both the CIAS plant and a slightly modified plant where the hot water supply to the load is adjusted constant at times when the water temperature from tank may exceed the set temperature. It is found that the latter configuration has better thermal and economic performances over the conventional design.     

基于超效率DEA和Malmquist指数的三北地区风电经济效益评价

文章采用我国三北地区2009~2012年相应数据,构建超效率DEA和Malmquist指数模型对其风电投资效益进行测度和比较。结果表明:西北地区综合技术效率明显低于东北与华北地区,其中规模效率是影响风电综合技术效率高低的关键因素;另外,区域间技术进步指数的悬殊是造成三北地区风电经济效益差异明显的主要原因。最后提出各地区应该加强技术开拓,提高风电规模效率,合理选择发电厂以减少弃风现象等建议。     

Performance and economic analysis of air flow windows in a tropical climate

An experimental study was conducted in Thailand to determine the thermal performance of twin glazed windows with dynamic insulation. The effects of blinds situated either between or outside the glazing were analysed. With an external blind, the heat transfer coefficient was 1–25 W/m²°C with natural convection and 0–6 W/m²°C for a flow of 20m³/h (glass area = 2–16m²). The solar flux transmitted was evaluated analytically and experimentally depending on the blind's position. An economic study was performed on a six-sotrey air-conditioned building in Thailand. It showed in tropical countries that it may be more economical to use air flow windows than to have tinted single or double glass windows.     

Life cycle cost and energy analysis of a Net Zero Energy House with solar combisystem

The Net Zero Energy House (NZEH) presented in this paper is an energy efficient house that uses available solar technologies to generate at least as much primary energy as the house uses over the course of the year. The computer simulation results show that it is technically feasible to reach the goal of NZEH in the cold climate of Montreal. In terms of the life cycle energy use, which considers the operating and embodied energy of the house, the energy payback time is 8.4–8.7 years, when the NZEH is compared with an average house that complies with the provincial code. The energy payback ratio of the combisystem is 3.5–3.8 compared with the heating system of conventional house. By converting solar energy, the combisystem supplies at least 3.5 times more energy than the energy invested for manufacturing and shipping the system. The life cycle cost analysis of the NZEH shows, however, that due to the high cost of the solar technologies and the low cost of electricity in Montreal, financial payback is never achieved.     

Technical and economic analysis of electricity generation from forest, fossil, and wood-waste fuels in a Finnish heating plant

The Finnish energy industry is subject to policy decisions regarding renewable energy production and energy efficiency. Conventional electricity generation has environmental side-effects that may cause global warming. Renewable fuels are superior because they offer near-zero net emissions.In this study, I investigated a heating mill’s ability to generate electricity from forest fuels in southern Finland on a 1-year strategic decision-making horizon. I solved the electricity generation problem using optimization of the energy products and fuel mixtures based on energy efficiency and forest technology. The decision environment was complicated by the sequence-dependent procurement chains for forest fuels. The optimal product and fuel mixtures were selected by minimizing procurement costs, maximizing production revenues, and minimizing energy losses.The combinatorial complexity of the problem required the use of adaptive techniques to solve a multiple-objective linear programming system with industrial relevance. I discuss the properties of the decision-support system and methodology and illustrate pricing of electricity generation based on real industrial data. The electricity-generation, -purchase, and -sales decisions are made based on a comprehensive technical and economic analysis that accounts for procurement of local forest fuels in a holistic supply chain model.     

Transport,travel and energy in the UK Trend analysis of published statistics

Transport is the only major sector where there has been an increase in energy consumption over the last 10 years. This article concentrates on the road and rail sectors and presents for the firts time an intermodal comparison of the trends on a time-series basis. The underlying reasons are explored and some of the complex interactions between individual factors highlighted. Several options for reducing energy consumption in the transport sector are proposed. Given the efficacy of oil for transport, there is only a limited opportunity for improvements in the existing stock of vehicles (through measures such as increases in car occupancy) and technological improvements offer the best alternative.