BIPV for the high-temperature, high-rise, high-density cities of S. China: The related projects of PV HKU research group to facilitate BIPV application

In cities where high-rise commercial developments have overtaken industry as the peak electricity consumer, sophisticated building integrated photovoltaics (BIPV) can offset the demand by generating electricity during daytime peak consumption. The PV HKU Research Group's related projects, in a triple strategy of Technology Assessment, Technology Application & Regulatory Framework, aims to provide the government and community with the information, experience and appropriate legislation to facilitate widespread BIPV applications, and assist compliance with the Kyoto Protocol on CO₂ emissions reduction.     

The effect of using two PCMs on the thermal regulation performance of BIPV systems

Building Integrated Photovoltaics (BIPVs) is one of the most promising applications for Photovoltaics (PVs). However, when the temperature in the BIPV increases, the conversion efficiency deteriorates. A PV/PCM system using Phase Change Materials (PCM) for BIPV thermal control has been experimentally and numerically studied previously. One of the main barriers for this application is how to improve the low thermal conductivity of the PCM in order to achieve a quick thermal dissipation response with longer thermal regulation in PVs. Although the metal fins inserted inside the PCM can improve the heat transfer, the thermal regulation period declines as the volume of the PCM is substituted by the metal mass of the PV/PCM system. A modified PV/PCM system integrated with two PCMs with different phase transient temperatures for improving the heat regulation needs to be investigated. The use of combinations of PCMs, each with a set of different phase transient temperatures, is expected to enhance the thermal regulation effect of the PV/PCM system and lengthen the thermal regulation time in PVs. In this study a developed PV/PCM numerical simulation model for single PCM application has been modified to predict the thermal performance of the multi-PCMs in a triangular cell in the PV/PCM system. A series of numerical simulations tests have been carried out in static state and realistic conditions in UK. The thermal regulation of the PV/PCM system with a different range of phase transient temperature PCMs has been discussed.     

Practical application of building integrated photovoltaic (BIPV) system using transparent amorphous silicon thin-film PV module

An analysis has been carried out on the first practical application in Korea of the design and installation of building integrated photovoltaic (BIPV) modules on the windows covering the front side of a building by using transparent thin-film amorphous silicon solar cells. This analysis was performed through long-term monitoring of performance for 2 years. Electrical energy generation per unit power output was estimated through the 2 year monitoring of an actual BIPV system, which were 48.4 kWh/kWp/month and 580.5 kWh/kWp/year, respectively, while the measured energy generation data in this study were almost half of that reported from the existing data which were derived by general amorphous thin-film solar cell application. The reason is that the azimuth of the tested BIPV system in this study was inclined to 50° in the southwest and moreover, the self-shade caused by the projected building mass resulted in the further reduction of energy generation efficiency. From simulating influencing factors such as azimuth and shading, the measured energy generation efficiency in the tested condition can be improved up to 47% by changing the building location in terms of azimuth and shading, thus allowing better solar radiation for the PV module. Thus, from the real application of the BIPV system, the installation of a PV module associated with azimuth and shading can be said to be the essentially influencing factors on PV performance, and both factors can be useful design parameters in order to optimize a PV system for an architectural BIPV application.     

Life cycle assessment of a solar thermal collector: sensitivity analysis, energy and environmental balances

Starting from the results of a life cycle assessment of solar thermal collector for sanitary warm water, an energy balance between the employed energy during the collector life cycle and the energy saved thanks to the collector use has been investigated. A sensitivity analysis for estimating the effects of the chosen methods and data on the outcome of the study was carried out. Uncertainties due to the eco-profile of input materials and the initial assumptions have been analysed.Since the study is concerned with a renewable energy system, attention has been focused on the energy indexes and in particular the “global energy consumption”. Following the principles of Kyoto Protocol, the variations of CO₂ emissions have also been studied.     

Prospective life cycle carbon abatement for pyrolysis biochar systems in the UK

Life cycle assessment (LCA) of slow pyrolysis biochar systems (PBS) in the UK for small, medium and large scale process chains and ten feedstocks was performed, assessing carbon abatement and electricity production. Pyrolysis biochar systems appear to offer greater carbon abatement than other bioenergy systems. Carbon abatement of 0.7–1.3 t CO₂ equivalent per oven dry tonne of feedstock processed was found. In terms of delivered energy, medium to large scale PBS abates 1.4–1.9 t CO₂e/MWh, which compares to average carbon emissions of 0.05–0.30 t CO₂e/MWh for other bioenergy systems. The largest contribution to PBS carbon abatement is from the feedstock carbon stabilised in biochar (40–50%), followed by the less certain indirect effects of biochar in the soil (25–40%)—mainly due to increase in soil organic carbon levels. Change in soil organic carbon levels was found to be a key sensitivity. Electricity production off-setting emissions from fossil fuels accounted for 10–25% of carbon abatement. The LCA suggests that provided 43% of the carbon in the biochar remains stable, PBS will out-perform direct combustion of biomass at 33% efficiency in terms of carbon abatement, even if there is no beneficial effect upon soil organic carbon levels from biochar application.     

Life cycle assessment and environmental life cycle costing analysis of lignocellulosic bioethanol as an alternative transportation fuel

The objective of this paper is to conduct Life Cycle Assessment (LCA) and Environmental Life Cycle Costing (ELCC) studies for lignocellulosic bioethanol blends [E10 and E85 (10% and 85% by volume of bioethanol with gasoline, respectively)] and conventional gasoline (CG). To compare the environmental performance and economic advantage of the selected fuel blends, the impact potentials and the cost of fuel applications per kilometer by a middle size car was evaluated. According the LCA results, one kilometer driven by E10 and E85 fueled vehicles could reduce the greenhouse gas (GHG) emissions by 4.3% and 47% and ozone layer depletion emissions by 3% and 66%, respectively, relative to CG. However, shifting from gasoline to bioethanol increases the emissions that contribute to eutrophication and photochemical ozone depletion. In terms of acidification potential, E85 shows a more favorable result relative to E10 and CG. According to the ELCC analysis, E85 fuel use provides a 23% lower driving cost relative to CG based on a-1 km driving distance. The results showed that E85 seems to be the best alternative in terms of both GHG emission and fuel production cost reduction compare to CG.     

An evaluation on the life cycle of photovoltaic energy system considering production energy of off-grade silicon

In this study, single-crystalline silicon (c-Si) photovoltaic (PV) cells and residential PV systems using off-grade silicon supplied from semiconductor industries were evaluated from a life cycle point of view. Energy payback time (EPT) of the residential PV system with the c-Si PV cells made of the off-grade silicon was estimated at 15.5 years and indirect CO₂ emission per unit electrical output was calculated at 91 g-C/kWh even in the worst case. These figures were more than those of the polycrystalline-Si and the amorphous-Si PV cells to be used in the near future, but the EPT was shorter than its lifetime and the indirect CO₂ emissions were less than the recent average CO₂ emissions per kWh from the utilities in Japan. The recycling of the c-Si PV cells should be discussed for the reason of the effective use of energy and silicon material.     

Parameters affecting the life cycle performance of PV technologies and systems

This paper assesses modeling parameters that affect the environmental performance of two state-of-the-art photovoltaic (PV) electricity generation technologies: the PVL136 thin film laminates and the KC120 multi-crystalline modules. We selected three metrics to assess the modules’ environmental performance, which are part of an actual 33 kW installation in Ann Arbor, MI. The net energy ratio (NER), the energy pay back time (E-PBT), and the CO₂ emissions are calculated using process based LCA methods. The results reveal some of the parameters, such as the level of solar radiation, the position of the modules, the modules’ manufacturing energy intensity and its corresponding fuel mix, and the solar radiation conversion efficiency of the modules, which affect the final analytical results. A sensitivity analysis shows the effect of selected parameters on the final results. For the baseline scenario, the E-PBT for the PVL136 and KC120 are 3.2 and 7.5 years, respectively. When expected future conversion efficiencies are tested, the E-PBT is 1.6 and 5.7 years for the PVL136 and the KC120, respectively. Based on the US fuel mix, the CO₂ emissions for the PVL136 and the KC120 are 34.3 and 72.4 g of CO₂/kW h, respectively. The most effective way to improve the modules’ environmental performance is to reduce the energy input in the manufacturing phase of the modules, provided that other parameters remain constant. Consequently, the use of PV as an electricity source during PV manufacturing is also assessed. The NER of the supplier PV is key for the performance of this scheme. The results show that the NER based on a PV system can be 3.7 times higher than the NER based on electricity supplied by the traditional grid mix, and the CO₂ emissions can be reduced by 80%.     

A well to pump life cycle environmental impact assessment of some hydrogen production routes

In the present study, a comparative well to pump life cycle assessment is conducted on the hydrogen production routes of water electrolysis, biomass gasification, coal gasification, steam methane reforming, hydrogen production from ethanol and methanol. The CML 2001 impact assessment methodology is employed for assessment and comparison. Comparatively higher life cycle Carbon dioxide and Sulphur oxide emissions of 27.3 kg/kg H₂ and 50.0 g/kg H₂ respectively are determined for the water electrolysis hydrogen production route via U.S. electricity mix. In addition, the life cycle global warming potential of this route (28.6 kg CO_2eq/kg H₂) is found to be comparatively higher than other routes followed by coal gasification (23.7 kg CO_2eq/kg H₂)_. However, the ethanol based hydrogen production route is estimated to have comparatively higher life cycle emissions of nitrogen dioxide (19.6 g/kg H₂) and volatile organic compounds (10.3 g/kg H₂). Moreover, this route is determined to have a comparatively higher photochemical ozone creation potential of 0.0045 kg-ethene_eq/kg H₂ as well as eutrophication potential of 0.0043 kg PO_4eq/kg H_2. The results of this study are comparatively discussed to signify the importance of life cycle assessment in comparing the environmental sustainability of hydrogen production routes.     

The energy consumption and environmental impacts of SCR technology in China

Energy and environment are drawing greater attention today, particularly with the rapid development of the economy and increase consumption of energy in China. At present, coal-fired power plants are mainly responsible for atmospheric air pollution. The selective catalytic reduction (SCR) technology is a highly effective method for NO_X control. The present study identified and quantified the energy consumption and the environmental impacts of SCR system throughout the whole life cycle, including production and transportation of manufacturing materials, installation and operation of SCR technology. The analysis was conducted with the utilization of life cycle assessment (LCA) methodology which provided a quantitative basis for assessing potential improvements in the environmental performance of the system. The functional unit of the study was 5454 t NO_X emission from an existing Chinese pulverized coal power plant for 1 year. The current study compared life cycle emissions from two types of de-NO_X technologies, namely the SCR technology and the selective non-catalytic reduction (SNCR) technology, and the case that NO_X was emitted into atmosphere directly. The results showed that the environmental impact loading resulting from SCR technology (66810 PET₂₀₀₀) was smaller than that of flue gas emitted into atmosphere directly (164121 PET₂₀₀₀) and SNCR technology (105225 PET₂₀₀₀). More importantly, the SCR technology is much more effective at the elimination of acidification and nutrient enrichment than SNCR technology and the case that NO_X emitted into atmosphere directly. This SCR technology is more friendly to the environment, and can play an important role in NO_X control for coal-fired power plants as well as industrial boilers.     

Economics, environment, and energy life cycle assessment of automobiles fueled by bio-ethanol blends in China

This study examines the life cycle economics, environment impacts, and energy consumptions of Chinese automobiles fueled by bio-ethanol blends, utilizing life cycle assessment (LCA) techniques, and puts forward C, Env, En, EEE indicators to assess the economics, combined environmental impacts, energy consumption, and the balance of the three, as a means to evaluate whether the energy utilization efficiency and the domestic environment improvement are achieved at the lowest cost possible. A generic gasoline fueled car is used as a baseline case, and the cassava-based E85 fueled FFV in Guangxi is used as a case study. On the life cycle basis, the cost of cassava-based E85 fueled FFV is about 15% higher than that of gasoline fueled car, of which the two key factors are the price of cassava and gasoline, through a cost breakdown analysis. It also has lower life-cycle emissions of CO₂, CO, HC, and PM pollutants, higher NO_X emissions, while about 20% combined environment indicator is lower than that of the gasoline fueled car. And, it is higher in total energy consumption, lower in fossil fuels and petroleum consumptions, and has a better combined energy indicator. Lastly, the EEE indicator of the cassava-based E85 fueled FFV is about 29% less than that of the gasoline fueled car. Hence, E85 fueled FFV is a better vehicle than the gasoline fueled car, taking the balance of all the 3 “E”s, the energy, environmental and economical aspects, into considerations.     

Reduction of energy consumption in biodiesel fuel life cycle

Essential requirements for biofuel are that (a) it should be produced from renewable raw material, and (b) it should have a lower negative environmental impact than that of fossil fuels. Apart from direct assessment of the engine emissions, environmental impact is also determined by performing life cycle analysis. Life cycle energy balance depends on specific climatic conditions and the agro- and processing technologies used. Rapeseed oil methyl ester life cycle energy ratios in Lithuanian conditions have been calculated as a function of rapeseed productivity, oil pressing and transesterification technologies used.Opportunities to improve biodiesel fuel life cycle energy efficiency, by implementing new technologies in agriculture as well as in industrial processing, were reviewed. The effectiveness of new technologies was evaluated on the basis of energy balance comparison.     

Life cycle environmental and economic analyses of a hydrogen station with wind energy

This study aimed to identify the environmental and economic aspects of the wind-hydrogen system using life cycle assessment (LCA) and life cycle costing (LCC) methodologies. The target H₂ pathways are the H₂ pathway of water electrolysis (WE) with wind power (WE[Wind]) and the H₂ pathway of WE by Korean electricity mix (WE[KEM]). Conventional fuels (gasoline and diesel) are also included as target fuel pathways to identify the fuel pathways with economic and environmental advantages over conventional fuels. The key environmental issues in the transportation sector are analyzed in terms of fossil fuel consumption (FFC), regulated air pollutants (RAPs), abiotic resource depletion (ARD), and global warming (GW). The life cycle costs of the target fuel pathways consist of the well-to-tank (WTT) costs and the tank-to-wheel (TTW) costs. Moreover, two scenarios are analyzed to predict potential economic and environmental improvements offered by wind energy-powered hydrogen stations.     

Life cycle assessment as a policy-support tool: The case of taxis in the city of Madrid

This paper examined the potentialities of Life Cycle Assessment (LCA) as instrument for policy-support. To this respect, the adoption of an initiative within the Madrid Air Quality Plan (AQP) 2011–2015 regarding the substitution of diesel taxis with hybrid, natural gas and LPG alternatives was studied. Four different scenarios were elaborated, a business-as-usual scenario (BAU), the scenario of the AQP, and two extreme-situation scenarios: all-diesel (ADI) and all-ecologic (AEC). Impacts were characterized according to the ILCD methodology, focusing especially on climate change (CC) and photochemical ozone formation (PO). SimaPro 7.3 was used as analysis and inventory-construction tool. The results indicate that the shift to ecologic alternatives reduced impacts, especially those related to CC and PO. For the complete life cycle, reductions of 13% (CC) and 25% (PO) were observed for AQP against BAU (CC:1365 Gg_CO2, PO:13336 Mg_NMVOC). Deeper reductions were observed for AEC (CC:34%, PO:59%), while ADI produced slight increases in impacts if against BAU. The analysis of the use-phase revealed that the central and highest speed zones of the city benefit from the adoption of AQP. This is especially evident in zone 7, with reductions of 16% in CC and 31% in PO respectively against BAU (CC_zone1:3443 kg_CO2/veh·km, PO_zone7:11.1 kg_NMVOC/veh·km).     

Energy analysis of an improved concept of integrated PV panels in an office building in central Greece

During the last decade, steel constructions with glazed façades became popular for commercial buildings in Greece. Moreover, expensive metal, natural stone, marble, ceramic, granite as well as special glass is employed for aesthetic and energy efficiency reasons. This creates opportunities for the introduction of Photovoltaic (PV) modules in double façades. PV modules on south-facing building walls are better placed at a distance from the wall to allow heat rejection and avoid overheating and efficiency loss. Exploiting the rejected heat of the PV modules is also a challenge. In this paper, we examine an improved concept of incorporating PV modules to the south façades of an office building, exploiting both the electricity produced and the heat rejected by the module, to increase building energy efficiency. The PV modules are integrated to the building wall by means of a double façade, which employs intervening ducts for ventilation purposes. The ducts are heating outdoor air, which is employed to cover the ventilation needs of the building, as well as a part of the heating loads. Simulations for typical winter and summer weather and solar insolation conditions are carried out to investigate the building’s energy performance improvements.     

The long-term life cycle private and external costs of high coal usage in the US

Using four times as much coal in 2050 for electricity production need not degrade air quality or increase greenhouse gas emissions. Current SO_x and NO_x emissions from the power sector could be reduced from 12 to less than 1 and from 5 to 2 million tons annually, respectively, using advanced technology. While direct CO₂ emissions from new power plants could be reduced by over 87%, life cycle emissions could increase by over 25% due to the additional coal that is required to be mined and transported to compensate for the energy penalty of the carbon capture and storage technology. Strict environmental controls push capital costs of pulverized coal (PC) and integrated coal gasification combined cycle (IGCC) plants to $1500–1700/kW and $1600–2000/kW, respectively. Adding carbon capture and storage (CCS) increases costs to $2400–2700/kW and $2100–3000/kW (2005 dollars), respectively. Adding CCS reduces the 40–43% efficiency of the ultra-supercritical PC plant to 31–34%; adding CCS reduces the 32–38% efficiency of the GE IGCC plant to 27–33%. For IGCC, PC, and natural gas combined cycle (NGCC) plants, the carbon dioxide tax would have to be $53, $74, and $61, respectively, to make electricity from a plant with CCS cheaper. Capturing and storing 90% of the CO₂ emissions increases life cycle costs from 5.4 to 11.6 cents/kWh. This analysis shows that 90% CCS removal efficiency, although being a large improvement over current electricity generation emissions, results in life cycle emissions that are large enough that additional effort is required to achieve significant economy-wide reductions in the US for this large increase in electricity generation using either coal or natural gas.     

Success factors of energy performance contracting (EPC) for sustainable building energy efficiency retrofit (BEER) of hotel buildings in China

Hotel building is a type of high-energy-consuming building and most existing hotel buildings need energy efficiency improvement in China. Energy performance contracting (EPC) is considered a win−win mechanism to organize building energy efficiency retrofit (BEER) project. However, EPC mechanism has been introduced into China relatively recently and many EPCs have not been successful in building energy efficiency retrofit projects. This research aims to develop a set of critical success factors (CSFs) of EPC for sustainable energy efficiency retrofit (BEER) of hotel buildings in China. Semi-structured interviews and a questionnaire survey with practitioners and other professionals were conducted. The findings reveal the relative importance of the 21 number of identified success factors. In order to explore the underlying relationship among the identified critical success factors (CSFs), factor analysis method was adopted for further investigation, which leads to grouping the 21 identified CSFs into six clusters. These are (1) project organization process, (2) EPC project financing for hotel retrofit, (3) knowledge and innovation of EPC, sustainable development (SD), and M&V, (4) implementation of sustainable development strategy, (5) contractual arrangement, and (6) external economic environment. Finally, several relevant policies were proposed to implement EPC successfully in sustainable BEER in hotel buildings.     

大中型沼气工程生命周期能效评价

基于生命周期评价理论,对山东某沼气工程进行了能效评价。研究得出,该沼气工程生命周期总能耗(折合标准煤)为561 471.47 kg/a(11.54 kg/GJ),其中,化石能耗占96.62%;节能量为1 100 271.42 kg/a;生命周期综合能源利用率为61.82%;生命周期新水耗量为26 552.56 m3/a。利用Sima Pro 8.0.2软件,采用生态指数法分析得出,该沼气工程生命周期产生的环境影响为364.303 3 k Pt/a(7.480 5 Pt/GJ);通过情景分析得出,沼气工程的环境损害减弱能力为191.805 2 k Pt/a(34.49%)。针对该沼气工程存在的一些问题,提出了开发沼液综合利用技术等建议,为提高沼气工程能效、减少环境损害提供理论参考。     

Economical and environmental impact of room air conditioners energy labels in Malaysia

The usage of residential electrical appliances for the last two decades has increased rapidly in Malaysia together with the increasing income per capita. Like other developing countries with hot and humid climates, Malaysia has been experiencing dramatic growth in the number of use of air conditioners, and the usage will be higher in the future. In order to reduce energy consumption in the residential sector, the Department of Electricity and Gas Supply considers implementing energy labels for room air conditioners sometime in the coming year. This study attempts to calculate the economical and environmental impact of implementing this program in Malaysia. The study found the savings has exceeded the investment cost and the program has reduced the emissions caused by burning fossil fuel.     

Life cycle energy and environmental assessment of bio-CNG utilization from cassava starch wastewater treatment plants in Thailand

Global warming, energy security, and the rising costs of oil have added a greater driving force to the development of feasible alternatives to petroleum-based transportation fuels. In parallel, wastes and wastewater generated from various industries should be avoided or converted to energy more in the future in order to reduce environmental problems and provide additional sources of energy. In this aspect, biogas plant is an effective option where gas is produced biologically by the fermentation of animal dungs, sewage, and agricultural residues. To utilize biogas as a transportation fuel, raw biogas has to undergo two major processes: cleaning and upgrading, to achieve natural gas quality. The upgraded biogas (so called bio-methane or bio-CNG) is considered green fuel with respect to environment, climate, and human health. However, the resulting bio-CNG from the processes still needs to be evaluated in terms of greenhouse gas emissions and energy aspects. This paper presents the integrated life cycle energy and environmental assessment of compressed bio-methane gas (CBG or bio-CNG) generated from cassava starch wastewater treatment plant in Thailand. The functional units were set to be 1 MJ of bio-CNG and 1 km of vehicle driven. The system boundary covered six main steps: digestion, purification and upgrading, compression, distribution, refueling, and combustion. The energy analysis result showed that the net energy ratio was higher than one, indicating a net energy gain. For the greenhouse gases aspect, the results showed that the biogas production and biogas upgrading step had the highest impact due to methane loss and high energy consumption. Comparing with other fuels, the global warming potential of bio-CNG was lower than those of fossil-based CNG and gasoline.