USE OF GAS-DRIVEN HEAT PUMPS, GROUND WATER AND RECOVERED HEAT IN TRINITY COLLEGE

Ziel

The use of low grade heat extracted from ground water to heat University Buildings using a novel combination of techniques, thus reducing the consumption of fuel-oil and mains water.
The fundamental objective is the use of electrical water-water heat pumps to replace conventional heating plant and to use rejected ground water in place of mains water. The investment cost is expected to be 695,124 IRL. The project has been reduced in scale because of unforseen technical difficulties. The predicted annual savings in fossil fuel based energy consumption are 1,009,000 kWh. As a result of this reduced scale, the main project is no longer justifiable in terms of payback. It is expected, however, that the lessons learned during the project will enable very much shorter payback periods to be achieved on similar future projects.
1. The initial plan involved the use of two large heat pumps (1055 kW and 703 kW). This was revised during the project to take account of advances in heat pump design and the findings of full scale ground water extraction tests.
2. Two 200 mm boreholes were drilled to a depth of approximately 30 m and ten 150 mm boreholes were drilled through the overburden and 1 m into the bedrock. The 150 mm boreholes were fully developed and pump tested. The extent of the acquifer was established and conclusive yield tests carried out.
3. A high precision survey of a number of existing buildings in the area was carried out to enable the effects of ground water extraction to be precisely monitored during the project.
4. One large diameter production well has been constructed, developed and tested. A low temperature pipeline network distributing ground water to five heat pumps has been installed.
5. Geological and geotechnical data analysis have confirmed the feasibility of extracting the required output of ground water. There has been no indication of any associated settlement of existing buildings.
6. The pump test data obtained to-date indicates that the production well is capable of sustaining an abstraction rate of 30 l/s for thirteen hours followed by a minimum recovery period of ten hours. This pumping regime closely matches the heat pump requirements as it is intended that they will not be operated when electrical loading is critical. It is also intended to maximise the use of the heat pumps during off-peak periods by "pre-heating" the building fabric. Ground water temperatures ranged from 11.4 C to 14.69 C. Design temperature has been taken as 12 C. The water is of marginal quality with regard to "domestic" consumption (tds 1,500 ppm). Salinity levels are such that some reverse osmosis treatment will almost certainly be necessary.
7. The first heat pump installed was used as a test facility to determine the feasibility of installing and controlling a heat pump connected directly into an existing heating system. This proved to be a complex and costly study, but enabled the College to devise a novel, low cost, design for future installations. It also confirmed the feasibility of operating electrically driven heat pumps at a COP of approximately 4.
8. The project was revised to take account of the delay and cost over-run incurred during the installation and testing of the first heat pump installation. The revised project consists of five heat pumps serving the Zoology Building, the Physics Building, the Botany Building and the O'Reilly Institute. The work in the Physics and Botany buildings has been completed and the final installation in the O'Reilly Institute was completed in 1989.
The project is being undertaken in the University of Dublin, Trinity College. The University employs approximately 1,400 staff and has a student population of approximately 8,000. It is located in the centre of the city of Dublin, housed in a mixture of historic and modern buildings with a gross floor area of approximately 110,000 m2.
Ground water will be extracted from a major aquifer located at the North East corner of the University campus and distributed via a low cost, low temperture (12 C) pipeline network to a number of medium sized electrically driven heat pumps. The aquifer consists of coarse alluvial gravels of up to 5 metres in depth lying on top of black boulder clay and covered with silts, sands and made ground. The aquifer lies between 3 and 8 metres below ground level. One large diameter production well will provide ground water at approximately 12 C for distribution to electrically driven heat pumps with outputs ranging from 60 kW to 130 kW. These heat pumps are designed to operate with a coefficient of performance in excess of 4 by chilling the ground water to 7 C and supplying water at 55 C directly to existing heating systems. Peak heating loads in extreme weather conditions will be met using existing oil and gas fired boilers. A new control system being developed under contract number EE/557/86/IR will be used to minimise the use of existing boilers.
It is intended that the rejected water will be used, where practicable, for local cooling purposes. It is also intented to treat some of the rejected ground water centrally and to use it in place of mains water for "domestic" purposes. This aspect of the project is presenting the greatest economic difficulties because it will probably be necessary to reduce the salinity of the water prior to its use for "domestic" purposes.

Programm/Programme

ENG-ENALT 2C - Programme (EEC) of demonstration projects relating to the exploitation of alternative energy sources and to energy saving and the substitution of hydrocarbons, 1983-1985

Thema/Themen

3.1 - BUILDINGS

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

DEM - Demonstration contracts

Koordinator

UNIVERSITY OF DUBLIN

EU-Beitrag

Keine Daten

Adresse

TRINITY COLLEGE COLLEGE GREEN
2 Dublin
Irland

Gesamtkosten