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Combined cooling heat and power in supermarkets

Abstract With recent initiatives from the UK government on reduced energy use, energy efficient systems such as combined heat and power (CHP) have been considered for new applications, including supermarkets. In these commercial buildings, the seasonal demand for heat results in underutilisation of the CHP equipment, limiting the primary energy savings that may be achieved. To increase the utilisation time, it has been proposed that heat generated by the CHP unit could be used to power an absorption refrigeration system providing cooling for the refrigerated cabinets. The application of an integrated CHP/absorption scheme or combined cooling heat and power (CCHP) in the supermarket is the subject of this paper. The paper initially describes the cooling/heating/power requirements of a typical supermarket and then reviews a number of CCHP options involving the use of different cooling and engine technologies. The investigation calculates and compares the energy savings/capital costs of the different options against typical conventional supermarket technology.

The use of CHP and absorption cooling in cold storage

In recent years, it has become standard practice to consider combined heat and power (CHP) systems early in the design stage of commercial buildings. With new initiatives from the UK government on reduced energy use, energy efficient systems such as CHP have been considered for a wider application particularly within industrial building design. The viability of CHP in a typical cold storage application is described in this paper. The electrical energy and heating requirements are defined and used to assess the annual energy consumption of a traditional cold storage design using a thermal model. The analysis is then used to consider the economics of different CHP configurations, which includes an integrated CHP and absorption system used to provide chilled glycol for the cold storage facilities. The additional capital cost of each configuration is shown and this is used to calculate the payback period. The results show that an attractive payback period of approximately four years for a combined CHP and absorption system may be achieved.

A review of research concerning the use of PCMS in air conditioning and refrigeration engineering

Publisher Summary Phase Change Materials (PCMs), which are an alternative to sensible storage, are finding new inroads into the large air conditioning scheme applications. Several novel methods of applying phase change materials in cooling systems are employed to improve the energy saving potential of PCMs. This chapter presents a scheme where thermal storage is incorporated into the cooling tower circuit that enables the system to charge the thermal store at night when there are lower wet bulb temperatures. The stored cold energy is released into the heat rejection circuit during the day, which produces lower condensing temperatures and higher efficiency. This method can reduce both peak energy and power use by as much as 35%. The chapter also discusses a scheme that uses night sky radiant cooling within the heat rejection water circuit. The lower effective temperature of the night sky is used as a heat sink with long wave radiation taking place between the condenser water and the night sky. With the use of thermal storage cold energy can be released during daytime hours to improve energy efficiency.

Evaluation of an underground railway carriage operating with a sustainable groundwater cooling system

Abstract In London and Merseyside in the UK, which are served by deep underground railway networks, rising water tables are proving an increasing problem, leading to a serious deterioration of track, traction supply and signalling systems. Also in these transport systems there is an increasing demand for an energy efficient and environmentally sustainable comfort cooling system. This paper outlines a novel cooling system that aims to reduce the water table by using the groundwater for ‘free’ cooling the railway network. This paper investigates the potential for cooling the underground network and trains in this way. It uses a purposely-developed mathematical model to show that additional cooling to the existing rolling stock may be provided, by cooling the tunnels within which they operate. It has been shown theoretically, that by cooling the air within the tunnels by 9K, the temperature in the typical carriage operating under peak load conditions will reduce by approximately 6K to a much more acceptable level. Finally the paper identifies areas for further work, that are required in order to realise the preferred way of achieving a sustainable cooling scheme.

Cooling microprocessors using vapor compression refrigeration

Maintaining future high performance microprocessor chips within an acceptable operating temperature range (e.g. less than 85°C), is likely to involve the removal of large quantities of heat (e.g. several hundred Watts), from small areas (e.g. 1– 2 cm2), necessitating very high heat fluxes. To date, heat dissipation from computer chips has generally been achieved by means of heat sinks and fans; however, alternative, more effective cooling techniques are likely to be needed in the future. Three UK universities are undertaking a 3-year collaborative project to develop a miniature vapor compression refrigeration (VCR) system, suitable for future microprocessor and electronic cooling. The design and testing of a novel porous media based evaporator heat exchanger is being undertaken by Newcastle University. Preliminary results suggest that this device should be capable of achieving the high heat fluxes required. The University of Oxfords Cryogenics Group has developed specialised oil-free compressors for low temperature cooling systems for space applications. Based on this work, a new design of compressor has been developed, which is suitable for use with miniature VCR devices. The performance of such systems is being studied by means of simulation by London South Bank University. Models developed to date include an overall miniature VCR system model, and a detailed model of the compressor. The current paper will focus on the design and construction of the compressor and the compressor model developed. The mathematical modelling approach used will be discussed, and the results from a number of simulations will be reported.

Investigation of an integrated low carbon solar assisted heat pump

© 2016, International Institute of Refrigeration. All rights reserved.Solar Assisted Heat Pumps have the potential to provide low carbon heat for domestic hot water generation and low temperature heating. They have advantages over conventional solar thermal systems because they can generate heating and hot water during periods of low or zero solar, whist still maintain the advantage of not needing to be connected to the gas grid. They are simple in nature and can be installed in a wide range of applications. They are also currently uncommon in the UK so a thorough understanding of the operating performance and characteristics is required. This is potentially an important energy technology that can be used to reduce heating energy consumption and reduce CO2 equivalent emissions in buildings. The paper describes the technology and presents an investigation in an office application. It describes an experimental investigation of solar assisted heat pumps which gives the relative performance compared to conventional methods.

Carbon reduction opportunities for supermarkets

Refrigeration is the largest load in a supermarket, accounting for 50-60% of the electricity consumption. Supermarket refrigeration systems also generate greenhouse gas emissions directly through refrigerant leakage. Technologies that can save direct and indirect emissions in a typical baseline UK supermarket were examined and the application timescales and cost per tonne of CO2abated were calculated using a model of the supermarket. Using the model, the technologies that could save the most carbon were identified. The work examined 81 different technologies and their potential to save direct and indirect emissions in supermarkets. Results from the work have shown that most technologies either save CO2eemissions from reduction in energy or from reduction in refrigerant leakage only a few technologies demonstrated savings from both.

Overview of Sustainable Refrigerated Road Transport Systems

As the global demand for refrigerated products increase, it has become progressively challenging to develop sustainable refrigerated road transport systems. Manufacturers and fleet operators have to balance the competing interests of maintaining temperature control while reducing the energy consumption and overall environmental impact of these systems. This article provides an overview of the general requirements of refrigerated road transport vehicles. It analyses the design of the vehicle temperature storage compartment and the refrigeration equipment, as well as various controls and strategies used to improve the performance and design of the system. It also reviews a range of modelling techniques, experiments and laboratory tests used to evaluate key factors which influence the condition of the air in the refrigerated space, energy consumption, cost and environmental impact.

A summary of the proceedings of the UK Institute of Refrigeration 1998/1999

This paper provides a short review of seven technical papers that have been presented to members of the United Kingdoms Institute of Refrigeration between October 1998 and April 1999. The aim of the paper is to provide wider dissemination of research and development work within the UKs refrigeration community. The subjects covered include current research into air cycle air conditioning, liquid pressure amplification, the application of wide boiling refrigerants and optimum display conditions for unwrapped chilled food. Also included are papers on recent developments in thermosyphon cooling, the opportunities for chilled ceilings and beams, and this publication is concluded with a paper by a consultant providing up to date guidance on measures to improve refrigeration plant performance.