mCHP Unit Research Articles

Validated dynamic energy model for a Stirling engine μ-CHP unit using field trial data from a domestic dwelling

This paper presents the development and validation of a dynamic energy performance model for a WhisperGen Stirling engine micro-CHP (μ-CHP) Mk 4 unit. The model is based on empirical equations for different system characteristics (start-up, continuous operation and shutdown) developed using measured performance data. The model was implemented using MatLab program and its validation was undertaken against measured performance data from a unit installed in a dwelling under field trial in Northern Ireland. Given a heat demand profile for a domestic dwelling, the model can be used to predict the heat and electricity output. Using heat and electricity data for a dwelling over a period of 1 month, the model over-predicted the total electrical and thermal energy output from the μ-CHP unit by 1.4% and 4.2% respectively. The model predicted the electrical power output with a mean absolute error of 7.4% and a cumulative over-prediction of 4.7%. The thermal power output was predicted with a mean absolute error of 7.2% and a cumulative under-prediction of 3.7%.

Analysis of the impact of heat-to-power ratio for a SOFC-based mCHP system for residential application under different climate regions in Europe

In this paper, the ability of a micro combined heat and power (mCHP) system to cover the heat and electricity demand of a single-family residence is investigated. A solid oxide fuel cell based mCHP system coupled with a hot water storage tank is analyzed. The energy profiles of single-family households in different European countries are evaluated. The range of Heat-to-Power Ratio for the SOFC-based mCHP System of 0.5–1.5 shows good agreement with the hot water, space heating and electricity demand during the warm seasons across Europe. This suggests that the fuel cell system should be sized according to the summer energy demand. The winter energy demand shows a Heat-to-Power Ratio which cannot be covered by the mCHP unit alone. To ensure that the mCHP system meets both the thermal and electrical energy demand over the entire year, an auxiliary boiler and a hot water storage tank need to be coupled with the mCHP unit. It is further noted that the size of the auxiliary boiler should match the larger winter space heating demand. In contrast, the hot water tank volume should be sized according to the warm season space heating requirement, when space heating is not required but electricity and hot water are still in demand. This maximizes the running time of the fuel cell, and thus the economic and environmental benefit of the system, without wasting produced heat.

Modelling of a housing estate with micro-combined heat and power for power flow studies

A high concentration of micro-combined heat and power (mCHP) units leads to difficulties in predicting power flows in low-voltage electrical feeders. A simple model of a house with mCHP generation, which is combined with an estate model, is used to predict electrical network flows. The model of the estate includes representation of the residents’ behaviour and ambient weather conditions. Results for an individual house, as well as electrical power flows for the estate feeder, are shown for three different seasons of a year.

Agent-based control of distributed electricity generation with micro combined heat and power—Cross-sectoral learning for process and infrastructure engineers

For the distributed control of an electricity infrastructure incorporating clusters of residential combined heat and power units (micro-CHP or μCHP) a multi-agent system approach is considered. The network formed by households generating electricity with μCHP units and the facilitating energy supplier can be regarded as an electricity production system, analogous to a (flexible) manufacturing system. Next, the system boundary is extended by allowing the trade of electricity between networks of households and their supplier. A methodology for designing an agent-based system for manufacturing control is applied to both cases, resulting in a conceptual design for a control system for the energy infrastructure. Because of the analogy between production systems and infrastructures process systems engineering (PSE) approaches for optimisation and control can be applied to infrastructure system operations. At the same time we believe research on socio-technical infrastructure systems will be a valuable contribution to PSE management strategies.

Experimental analysis of micro-cogeneration units based on reciprocating internal combustion engine

The cogeneration, or the combined production of electric and/or mechanical and thermal energy, is a well-established technology now, which has important environmental benefits and has been noted by the European Community as one of the first elements to save primary energy, to avoid network losses and to reduce the greenhouse gas emissions. In particular, our interest will be focused on the micro-cogeneration, MCHP (electric power ≤15 kW), which represents a valid and interesting application of this technology which refers, above all, to residential and light commercial users [M. Dentice d’Accadia, M. Sasso, S. Sibilio, Cogeneration for energy saving in household applications, in: P. Bertoldi, A. Ricci, A. de Almeida (Eds.), Energy Efficiency in Household Appliances and Lighting, Springer, Berlin, 2001, pp. 210–221; Directive 2004/8/EC of the European Parliament and of the Council of the 11 February 2004 on the promotion of cogeneration based on the useful heat demand in the internal energy market and amending Directive 92/42/EEC, Official Journal of the European Union (2004)]. In particular, our work group started a R&D programme on micro-cogeneration in 1995: a laboratory, equipped with the most common appliances (washing-machine, dishwasher, storage water heater, …), has been built and some MCHP prototypes have been tested too. In this article, the results of an intense experimental activity on three different micro-cogenerators, one of them made in Japan and in a pre-selling phase, are reported. In a previous paper a detailed analysis of the test facility, with the description of the equipments and the data acquisition systems, can be found [M. Dentice d’Accadia, M. Sasso, S. Sibilio, R. Vanoli, Micro-combined heat and power in residential and light commercial applications, Applied Thermal Engineering 23 (2003) 1247–1259]. A typical 3-E (Energetic, Economic and Environmental) approach has been performed to compare the proposed energy system, MCHP, to the conventional one based on separate “production”. In the energetic analysis the amount of primary energy savings provided by micro-cogeneration unit has been evaluated for different types of MCHP units and at various working conditions. Furthermore the evaluation of the equivalent CO 2 emissions of the compared systems, MCHP and conventional systems, allows to calculate the MCHP potentials to reduce greenhouse gas emissions. Finally the Simple Pay Back approach has been considered to define the economic feasibility of cogeneration in small size applications with the varying of some economic variables (first cost, gas price, operating hours per year …).