Greenhouses on building roofs using heat from ventilating air

A case is proposed for rational use of exhaust ventilation as a heat source for roof mounted greenhouses which would add significantly to agricultural land resources with little adverse effect on urban life and minimum energy use.     

Selection of a trigeneration system using a fuzzy AHP multi‐criteria decision‐making approach

Owing to the wide range of trigeneration systems suitable for small‐scale applications, the selection of the optimal system according to the end users' requirements and environmental conditions is crucial. The evaluation and comparison of possible alternatives of trigeneration systems are a multi‐criteria decision problem because not only economic aspects must be considered but also technical, environmental and social aspects. This paper presents the case of selection of a trigeneration system for a typical residential building. Several kinds of trigeneration systems, whose dynamical sources are Stirling engines, micro‐turbines, reciprocating engines and fuel cells, respectively, and a separate generation system are evaluated and compared in detail. As the evaluation criteria are a mixture of quantitative and qualitative criteria, quantitative multi‐criteria methods are inadequate for handling this type of problems. Therefore a multi‐criteria decision‐making method, which combines the subjectivity of decision maker and the objectivity of numerical data, based on Fuzzy Set Theory and Analytic Hierarchy Process is proposed to solve this selection problem. Copyright © 2010 John Wiley & Sons, Ltd.     

Process synthesis and economics of combined biomethanol and CHP energy production derived from biomass wastes

BACKGROUND: This paper reports on process synthesis and economics of combined methanol and CHP (combined heat and power) energy production from crude biooil, waste glycerol produced in biodiesel factories and biomass wastes using integrated reactor design for hydrogen rich syngas. This new process consists of three process steps: (a) pyrolysis of organic waste material to produce biooil, char and pyrogas; (b) steam assisted hydrogasification of the crude glycerol wastes, biooil mixed with pyrogas for hydrogen rich gas; and (c) a low temperature methanol synthesis process. The H₂‐rich gas remaining after methanol synthesis is recycled back to the pyrolysis reactor, the catalytic hydro‐gasification process and the heat recovery steam generator (HRSG). RESULTS: The breakeven price of the Hbiomethanol process yields positive net financial NPV and IRR above 600 USD per tonne. The total capital cost for a small‐scale methanol plant of capacity 2 tonne h^?1 combined with a cogeneration plant of capacity 2 MWe power is estimated to be 170.5 million USD. CONCLUSION: Recycling gas allows the methanol synthesis reactor to perform at a relatively lower pressure than conventionally while the plant still maintains a high methanol yield. The integrated hydrogasification reactor and energy recovery design process minimizes heat loss and increases the process thermal efficiency. The Hbiomethanol process can convert any condensed carbonaceous material and liquid wastes, to produce methanol and CHP. Copyright © 2012 Society of Chemical Industry     

发展溴化锂吸收式空调实现冷热电联产

世界工业发达国家已经从热电联产(CHP)向冷热电联产(CCHP)发展,以提高能源利用效率和减轻环境污染及温室效应.我国除着手发展冷热电联产的同时,宜将已建成的热电厂,根据需要利用溴化锂吸收式空调改造成为冷热电联产,以提高热电厂的经济效益.     

Australian coal mine methane emissions mitigation potential using a Stirling engine-based CHP system

Methane, a major contributor to global warming, is a greenhouse gas emitted from coal mines. Abundance of coal mines and consequently a considerable amount of methane emission requires drastic measures to mitigate harmful effects of coal mining on the environment. One of the commonly adopted methods is to use emitted methane to fuel power generation systems; however, instability of fuel sources hinders the development of systems using conventional prime movers. To address this, application of Stirling engines may be considered.Here, we develop a techno-economic methodology for conducting an optimisation-based feasibility study on the application of Stirling engines as the prime movers of coal mine CHP systems from an economic and an environmental point of view. To examine the impact of environmental policies on the economics of the system, the two commonly implemented ones (i.e. a carbon tax and emissions trading scheme) are considered. The methodology was applied to a local coal mine. The results indicate that incorporating the modelled system not only leads to a substantial reduction in greenhouse gas emissions, but also to improved economics. Further, due to the heavy economic burden, the carbon tax scheme creates great incentive for coal mine industry to address the methane emissions.     

Intermediate temperature solid oxide fuel cell based on lanthanum gallate electrolyte

The Kansai Electric Power Co. Inc. (KEPCO) and Mitsubishi Materials Corporation (MMC) have been developing intermediate temperature solid oxide fuel cells (IT-SOFCs) which are operable at a temperature range between 600 and 800 °C. There are some significant features in IT-SOFC of KEPCO–MMC: (1) highly conductive lanthanum gallate-based oxide is adopted as an electrolyte to realize high-performance disk-type electrolyte-supported cells; (2) the cell-stacks with seal-less structure using metallic separators allow residual fuel to burn around the stack and the combustion heat is utilized for thermally self-sustainable operation; (3) the separators have flexible arms by which separate compressive forces can be applied for manifold parts and interconnection parts. We are currently participating in the project by New Energy and Industrial Technology Development Organization (NEDO) to develop 10 kW-class combined heat and power (CHP) systems. In FY2006, a 10 kW-class module was developed, with which the electrical efficiency of 50%HHV was obtained based on DC 12.6 kW. In the first quarter of FY2007, the 10 kW-class CHP system using the module gave the electrical efficiency of 41%HHV on AC 10 kW and the overall efficiency of 82%HHV when exhaust heat was recovered as 60 °C hot water. Currently, the operation has been accumulated for about 2500 h to evaluate the long-term stability of the system.     

A review of integration strategies for solid oxide fuel cells

Due to increasing oil and gas demand, the depletion of fossil resources, serious global warming, efficient energy systems and new energy conversion processes are urgently needed. Fuel cells and hybrid systems have emerged as advanced thermodynamic systems with great promise in achieving high energy/power efficiency with reduced environmental loads. In particular, due to the synergistic effect of using integrated solid oxide fuel cell (SOFC) and classical thermodynamic cycle technologies, the efficiency of the integrated system can be significantly improved. This paper reviews different concepts/strategies for SOFC-based integration systems, which are timely transformational energy-related technologies available to overcome the threats posed by climate change and energy security.     

Exergetic analysis of an innovative small scale combined cycle cogeneration system

The purpose of this paper has been to carry out an exergetic analysis of an innovative natural gas (NG) combined cycle cogeneration system (150-kW_e, 192-kW_t). The combined cycle is composed of a reciprocating Internal Combustion Engine (ICE), which is used as the topping cycle, and a water Rankine cycle (RC), which operates on the exhaust gases from the ICE, as the bottoming cycle.     

Exergetic efficiency of high‐temperature‐lift chemical heat pump (CHP) based on CaO/CO2 and CaO/H2O working pairs

The use of reversible chemical reactions in recuperation of heat has gained significant interest due to higher magnitude of reaction heat compared to that of the latent or sensible heat. To implement chemical reactions for upgrading heat, a chemical heat pump (CHP) may be used. A CHP uses a reversible chemical reaction where the forward and the reverse reactions take place at two different temperatures, thus allowing heat to be upgraded or degraded depending on the mode of operation. In this work, an exergetic efficiency model for a CHP operating in the temperature‐level amplification mode has been developed. The first law and the exergetic efficiencies are compared for two working pairs, namely, CaO/CO₂ and CaO/H₂O for high‐temperature high‐lift CHPs. The exergetic efficiency increases for both working pairs with increase in task, T_H, decrease in heat source, T_M, and increase in condenser, T_L, temperatures. It is also observed that the difference in reaction enthalpies and specific heats of the involving reactants affects the extent of increase or decrease in the exergetic efficiency of the CHP operating for temperature‐level amplification. Copyright © 2012 John Wiley & Sons, Ltd.