Micro Combined Heat And Power Systems Research Articles

Micro Combined Heat and Power Systems – Evaluation of a Sample Application

The growing need for a secure, cost-effective, less polluting and efficient form of energy has contributed to an increasing interest in the use of micro combined heat and power (MCHP) systems. In this paper, the environmental performance and economic feasibility of a 1 kWe internal combustion engine (ICE) MCHP system in a one-family house was assessed and compared with the baseline scenario were residential energy demands are met with grid electricity and natural gas fired condensing boilers. The result of the analysis shows that MCHP systems present opportunities for savings in energy costs. Based on a social discount rate (SDR) of 5 % and a calculated 3259 operating hours, a simple payback period of about 4.8 years was derived as the time needed to recover the extra investment cost of the ICE unit. The result of the sensitivity analysis reveals that, both the running hours and price of electricity have significant effects on the payback period of the project. Considering the end of useful life period of the systems, MCHP offer a good replacement for conventional gas boilers of 90 % efficiency. However, their high initial costs (when compared to high efficiency condensing boilers), could be seen as the major factor hampering market diffusion. Also, considering the optimal environmental benefits, MCHP system produced more on-site CO2 emissions in reference to the condensing boiler but generally, annual CO2 emission is reduced by about 38 % when compared to the overall separate generation of heat and power scenario.

Microcogeneration in buildings with low energy demand in load sharing application

The paper investigates the introduction of a MCHP (Micro Combined Heat and Power) system in buildings with low energy demand with respect to the current building stock. A load sharing approach between a multifamily residential building and an office one is taken into account. Dynamic simulations are carried out in order to evaluate the thermo-economic performance of the analyzed system. Particular attention is given to the estimation of the electric load of the different users, as the economic profitability of a MCHP system is strongly influenced by the amount of self-consumed electricity. In order to analyze the influence of climatic conditions, two different geographical locations in Italy (Naples and Turin, having 1034 and 2617 heating degree days, respectively) are considered. The results of this study indicate that the installation of MCHP systems in buildings with low energy demand allows to increase the percentage of self-consumed electricity reducing the bidirectional electricity flow between the users and the external grid, as well as the impact on the grid itself due to the large diffusion of distributed generation systems.Moreover this study shows that the load sharing approach between users with different load profile leads to better energy, environmental and economic results with respect to a conventional system. The climatic conditions play an important role on the MCHP operational hours and hence on the thermo-economic performance of the system. The primary energy saving of the system located in Turin is equal to 8.8% with respect to 6.2% of the system located in Naples. Also the environmental performance, evaluated in terms of equivalent CO2 avoided emissions, are better in Turin (8.3%) than in Naples (6.7%). The economic analysis shows acceptable values of the pay-back period in presence of economic support mechanisms. The findings of this study show that the introduction of a MCHP system in load sharing approach leads to thermo-economics advantages even considering the lower heating needs of well-insulated buildings.

A Review on Microcogeneration National Testing Procedures

Several standard testing procedures were prepared or are in a developing phase in many countries, to provide methods for determining the performance of MCHP (Micro Combined Heat and Power) systems. This is due to the quick diffusion of microcogenerators worldwide, especially in the Japanese, European and North American markets, and to existing supporting mechanisms, that require the achievement of specific minimum energy performance.In the framework of Subtask B of Annex 54 of International Energy Agency, information about national standard testing procedures were gathered. In this paper, the main available national standards are summarized, and a comparison is performed.

Energy and CO 2 emissions performance assessment of residential micro-cogeneration systems with dynamic whole-building simulation programs

Micro-cogeneration, also termed micro combined heat and power (MCHP) or residential cogeneration, is an emerging technology with the potential to provide energy efficiency and environmental benefits by reducing primary energy consumption and associated greenhouse gas emissions. The distributed generation nature of the technology also has the potential to reduce losses due to electrical transmission and distribution inefficiencies and to alleviate utility peak demand problems. Detailed MCHP models for whole-building simulation tools, developed in Annex 42 of the International Energy Agency (IEA) Energy Conservation in Buildings and Community Systems Programme, have been used to conduct a performance assessment study for a number of micro-cogeneration systems and residential buildings. Annual non-renewable primary energy (NRPE) demand and CO 2-equivalent (CO 2-eq) emissions were determined by simulation for different cogeneration technologies, namely natural gas-fuelled solid oxide (SOFC) and polymer electrolyte membrane fuel cells, Stirling and internal combustion engines. These were compared to the reference system with a gas boiler and electricity supply from the grid. A ground-coupled heat pump system was also analysed for comparison. The cogeneration units were integrated in single and multi-family houses of different energy standard levels. Two different electricity generation mixes were considered: European mix and combined cycle power plant (CCPP). For the MCHP devices, detailed dynamic component models as well as simplified performance map models were used, developed and calibrated with either results from laboratory experiments or with manufacturer data. The simulations were performed using the whole-building simulation programme TRNSYS, using domestic hot water and electric demand profiles specified in IEA Annex 42. Combinations of three demand levels were analyzed. In NRPE demand, for the European electricity mix, most MCHP systems offered reductions (up to 34%) in comparison with the gas boiler reference system and crediting the electricity exported to the grid. For the CCPP electricity generation mix, the largest NRPE reductions resulted for the ground-coupled heat pump systems (up to 29%). The maximum reduction with a cogeneration system was 14%. In terms of CO 2-eq emissions, most cogeneration systems offered reductions for the European electricity mix (up to 22%). However, maximum reductions resulted for the heat pump system (23%). For the CCPP mix, maximum reductions by far again resulted for the heat pump systems (up to 29%). The maximum reduction for a cogeneration system was achieved with the ICE system in the single-family house (14%).