A study in the application of domestic solar assisted heat pumps for heating and cooling

In the present work, the more important parameters of the heat pump system and of solar assisted heat pump systems were analysed in a quantitative way. Ideal and real Rankine cycles applied to the heat pump, with and without subcooling and superheating were studied using practical recommended values for their thermodynamics parameters. Comparative characteristics of refrigerants here analysed looking for their applicability in heat pumps for domestic heating and their effect in the performance of the system. Curves for the variation of the coefficient of performance as a function of condensing and evaporating temperatures were prepared for R12. Air, water and earth as low-grade heat sources and basic heat pump design factors for integrated heat pumps and thermal stores and for solar assisted heat pump-series, parallel and dual-systems were studied. The analysis of the relative performance of these systems demonstrated that the dual system presents advantages in domestic applications. An account of energy requirements for space and hater heating in the domestic sector in the O.K. is presented. The expected primary energy savings by using heat pumps to provide for the heating demand of the domestic sector was found to be of the order of 7%. The availability of solar energy in the U.K. climatic conditions and the characteristics of the solar radiation here studied. Tables and graphical representations in order to calculate the incident solar radiation over a tilted roof were prepared and are given in this study in section IV. In order to analyse and calculate the heating load for the system, new mathematical and graphical relations were developed in section V. A domestic space and water heating system is described and studied. It comprises three main components: a solar radiation absorber, the normal roof of a house, a split heat pump and a thermal store. A mathematical study of the heat exchange characteristics in the roof structure was done. This permits to evaluate the energy collected by the roof acting as a radiation absorber and its efficiency. An indication of the relative contributions from the three low-grade sources: ambient air, solar boost and heat loss from the house to the roof space during operation is given in section VI, together with the average seasonal performance and the energy saving for a prototype system tested at the University of Aston. The seasonal performance as found to be 2.6 and the energy savings by using the system studied 61%. A new store configuration to reduce wasted heat losses is also discussed in section VI.

Investigation of gas engine driven heat pump systems

Heat pumps are becoming increasingly popular, but poor electricity generating efficiency limits the potential energy savings of electrically powered units. Thus the work reported in this thesis concerns the development of a range of gas engine driven heat pumps for industrial and commercial heating applications, which recover heat from the prime mover, normally rejected to waste. Despite the convenience of using proprietary engine heat recovery packages, investigations have highlighted the necessity to ensure the engine and the heat recovery equipment are compatible. A problem common •to all air source heat pumps is the formation of frost on the evaporator, which must be removed periodically, with the expenditure of energy, to ensure the continued operation of the plant. An original fluidised bed defrosting mechanism is proposed, which prevents the build-up of this frost, and also improves system performance. Criticisms have been levelled against the rotary sliding vane compressor, in particular the effects of lubrication, which is essential. This thesis compares the rotary sliding vane compressor with other machines, and concludes that many of these criticisms are unfounded. A confidential market survey indicates an increasing demand for heat pumps up to and including 1990, and the technical support needed to penetrate this market is presented. Such support includes the development of a range of modular gas engine driven heat pumps, and a computer aided design for the selection of the optimum units. A case study of a gas engine driven heat pump for a swimming pool application which provided valuable experience is included.

The development of heat recovery equipment from conception to commercialisation

A comprehensive survey of industrial sites and heat recovery products revealed gaps between equipment that was required and that which was available. Two heat recovery products were developed to fill those gaps: a gas-to-gas modular heat recovery unit; a gas-to-liquid exhaust gas heat exchanger. The former provided an entire heat recovery system in one unit. It was specifically designed to overcome the problems associated with existing component system of large design commitment, extensive installation and incompatibility between parts. The unit was intended to recover heat from multiple waste gas sources and, in particular, from baking ovens. A survey of the baking industry defined typical waste gas temperatures and flow rates, around which the unit was designed. The second unit was designed to recover heat from the exhaust gases of small diesel engines. The developed unit differed from existing designs by having a negligible effect on engine performance. In marketing terms these products are conceptual opposites. The first, a 'product-push' product generated from site and product surveys, required marketing following design. The second, a 'market-pull' product, resulted from a specific user need; this had a captive market and did not require marketing. Here marketing was replaced by commercial aspects including the protection of ideas, contracting, tendering and insurance requirements. These two product development routes are compared and contrasted. As a general conclusion this work suggests that it can be beneficial for small companies (as was the sponsor of this project) to undertake projects of the market-pull type. Generally they have a higher probability of success and are less capital intensive than their product-push counterparts. Development revealed shortcomings in three other fields: British Standards governing heat exchangers; financial assessment of energy saving schemes; degree day procedure of calculating energy savings. Methods are proposed to overcome these shortcomings.

A heat metering system for energy management on an industrial site

Faced with a future of rising energy costs there is a need for industry to manage energy more carefully in order to meet its economic objectives. A problem besetting the growth of energy conservation in the UK is that a large proportion of energy consumption is used in a low intensive manner in organisations where they would be responsibility for energy efficiency is spread over a large number of personnel who each see only small energy costs. In relation to this problem in the non-energy intensive industrial sector, an application of an energy management technique known as monitoring and targeting (M & T) has been installed at the Whetstone site of the General Electric Company Limited in an attempt to prove it as a means for motivating line management and personnel to save energy. The objective energy saving for which the M & T was devised is very specific. During early energy conservation work at the site there had been a change from continuous to intermittent heating but the maintenance of the strategy was receiving a poor level of commitment from line management and performance was some 5% - 10% less than expected. The M & T is concerned therefore with heat for space heating for which a heat metering system was required. Metering of the site high pressure hot water system posed technical difficulties and expenditure was also limited. This led to a ‘tin-house' design being installed for a price less than the commercial equivalent. The timespan of work to achieve an operational heat metering system was 3 years which meant that energy saving results from the scheme were not observed during the study. If successful the replication potential is the larger non energy intensive sites from which some 30 PT savings could be expected in the UK.

Energy conservation measures on an industrial site

World and UK energy resources and use are reviewed and the role of energy conservation in energy policy identified. In considering various energy conservation measures, a distinction is made between energy intensive and non-intensive industries and also between direct and indirect uses of energy. Particular attention is given to the non-intensive user of energy. Energy use on one such industrial site has been studied to determine the most effective energy saving measures in the short term. Here it is estimated that over 65% of energy is consumed for indirect purposes, mainly for heating and lighting buildings. Emphasis is placed on energy auditing techniques and those energy saving measures requiring greater technical, economic and organisational resources to secure their implementation. Energy auditing techniques include the use of aerial thermography and snow formation surveys to detect heat losses. Qualitative and quantitative interpretations are carried out, but restricted mainly to evaluating building roof heat losses. From the energy auditing exercise, it is confirmed that the intermittent heating of buildings is the largest and most cost effective fuel saving measure. This was implemented on the site and a heat monitoring programme established to verify results. Industrial combined heat and power generation is investigated. A proposal for the site demonstrates that there are several obstacles to its successful implementation. By adopting an alternative financial rationale, a way of overcoming these obstacles is suggested. A useful by-product of the study is the classification of industrial sites according to the nature of industrial energy demand patterns. Finally, energy saving measures implemented on the site are quantlfied using comparative verification methods. Overall fuel savings of 13% are indicated. Cumulative savings in heating fuel amount to 26% over four years although heated area increased by approximately 25%.

Drying processess in the United Kingdom:assessment of industrial energy utilisation and efficiency of drying systems and the modelling of drying characters using neural networks (BL)

Drying is an important unit operation in process industry. Results have suggested that the energy used for drying has increased from 12% in 1978 to 18% of the total energy used in 1990. A literature survey of previous studies regarding overall drying energy consumption has demonstrated that there is little continuity of methods and energy trends could not be established. In the ceramics, timber and paper industrial sectors specific energy consumption and energy trends have been investigated by auditing drying equipment. Ceramic products examined have included tableware, tiles, sanitaryware, electrical ceramics, plasterboard, refractories, bricks and abrasives. Data from industry has shown that drying energy has not varied significantly in the ceramics sector over the last decade, representing about 31% of the total energy consumed. Information from the timber industry has established that radical changes have occurred over the last 20 years, both in terms of equipment and energy utilisation. The energy efficiency of hardwood drying has improved by 15% since the 1970s, although no significant savings have been realised for softwood. A survey estimating the energy efficiency and operating characteristics of 192 paper dryer sections has been conducted. Drying energy was found to increase to nearly 60% of the total energy used in the early 1980s, but has fallen over the last decade, representing 23% of the total in 1993. These results have demonstrated that effective energy saving measures, such as improved pressing and heat recovery, have been successfully implemented since the 1970s. Artificial neural networks have successfully been applied to model process characteristics of microwave and convective drying of paper coated gypsum cove. Parameters modelled have included product moisture loss, core gypsum temperature and quality factors relating to paper burning and bubbling defects. Evaluation of thermal and dielectric properties have highlighted gypsum's heat sensitive characteristics in convective and electromagnetic regimes. Modelling experimental data has shown that the networks were capable of simulating drying process characteristics to a high degree of accuracy. Product weight and temperature were predicted to within 0.5% and 5C of the target data respectively. Furthermore, it was demonstrated that the underlying properties of the data could be predicted through a high level of input noise.