2016 ASHRAE Annual Conference

The GreenHP-project aims at developing a new, highly efficient urban heating system based on a high-capacity air-to-water heat pump for retrofitting multi-family houses and commercial buildings. For this purpose, a comprehensive multi-level research approach ranging from new heat pump component designs to advanced system integration concepts is pursued. The proposed GreenHP system will be operated with a natural refrigerant, will interact with large (renewable) energy systems, like the smart grid in particular, and will include renewable energy sources, like photovoltaic and solar thermal. Combining the expertise from leading European research institutes and industry partners allows an integration of advanced fan, compressor and heat exchangers in a compact system. Using the natural refrigerant R290, the consortium aims for a heat pump system with minimum environmental impact and a high operating efficiency to provide a heating capacity of 30kW. The refrigerant charge of the system is minimised by using aluminium micro-channel tubes in both condenser and evaporator. The use of aluminium for the condenser allows an improved heat exchange compared to conventional steel designs. On the air side of the evaporator highly efficient air fins are developed that are less sensitive to icing. Also the fan is optimised for better handling of icing conditions. A bionic distributor will take care to evenly load the micro-channel tubes of the evaporator with refrigerant. Additionally a new compressor concept is developed, which is integrated in a holistic control strategy for most efficient energy management. In a next step, the newly designed components will be assembled and tested according to international standards (e.g.: EN14825) at the accredited testing facilities at AIT. The tests will focus on the overall system design measuring and evaluating the performance of the GreenHP-pilot unit. The full paper deals with the general GreenHP-layout and presenting first results.

Traditional residential heating systems have become very efficient leaving little room for significant improvement. However, an alternative means of domestic heating was proposed that utilizes small scale power generation and space/hot water heating technologies known as micro-combined heat and power (mCHP) systems. These systems offer significant advantages to conventional heating systems including decreased energy usage, cost, and reduced CO₂ emissions. In addition, because these mCHP systems operate as distributed generation, they also reduce transmission losses and eliminate peak demand issues. These benefits come at the expense of complexities including matching the heat to power ratio for the residential sector and significant daily cycling, among other challenges.

Recently fuel cell based mCHP systems have been proposed as a means of providing both heat and power for the residential sector. These systems are meant for power generation at high efficiency and low emissions, but the heat can still be recovered for space or hot water heating. These systems are still under development and significant research is being conducted to determine if fuel cell based systems can match the load requirements of a typical household. Despite the work performed, different studies have had drastically different conclusions for the fate of fuel cell systems leaving many unanswered questions for the future.

A systematic review of current literature was undertaken to assess fuel cell based mCHP for the residential sector. The review highlighted many of the technical challenges facing these systems while also uncovering significant benefits and opportunities. In this paper, the results of the review are presented and an analysis of current trends and future priorities assessed. Fuel cell based mCHP is shown to have significant potential in reducing emissions and conserving natural resources while maintaining current building performance.

Energy consumption from commercial buildings is a major contributor of greenhouse gas emissions. In the UK, supermarkets consume 3% of the electricity and account for 1% of the country’s carbon emissions (Tassou et al. 2011). This paper explores the implementation of bio-methane fuelled combined heat and power (CHP) systems to satisfy heat and electricity demands of commercial buildings; with the overarching goal of making cost-effective investments and decarbonizing building operations. The research work consists in the development of a CHP technology selection and operation (TSO) optimization model. Results from this effort can be utilized to develop a strategy for investment in bio-methane CHP projects for a portfolio of supermarket buildings.

The TSO model enables a new approach for the selection and operation of CHP units that encompasses whole life costing, carbon emissions as well as half-hourly energy prices and demands throughout the day, seasonally and annually, providing a more comprehensive result than current methods. Utilising historic metered energy demands, projected energy prices and a portfolio of available CHP technologies, the mathematical model solves simultaneously for an optimal CHP unit selection and operational schedule for a determined building based on a preferred objective. The objective can either be: minimum cost, minimum GHG emissions, or a mix of both for an operational period that satisfies the store's energy demands. The model defines which unit to acquire and its power output for each half-hourly interval for different day types and a given time period.

The TSO model was implemented for a sample of 35 buildings from a group of over 1300 stores that belong to a supermarket chain in the UK. These varied in characteristics such as heat-to-power ratio, size, and electricity pricing region. It was identified that the majority of stores assessed could reduce their operational emissions more than 70% while providing returns on investment above 100% by installing low-carbon co-generation units. Results of this model prove that attractive cost and emissions savings are possible through the optimal selection and operation of CHP technologies fuelled by bio-methane.