Mine water as a Renewable Energy Resource - Promoscene

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Minewater as a Renewable Energy Resource Fig 3.6: Energy concept at Heerlen At first it had been hoped that the mine water would be at such useful temperatures for both space heating and cooling that, through low exergy design, no further energy input from more conventional low carbon technology would be required. However, for both the heating supply and the cooling supply it has proved necessary to include a heat pump. Although this means that the ratio between renewable mine water energy and electricity is not as favourable as had been hoped, heat pumps are themselves a low carbon technology so that the overall system should still achieve impressive carbon savings. A more serious problem is the emergence of the water for cooling at a higher temperature than expected. This together with much higher than expected pump consumption are teething problems that are under investigation. There also remains the need for domestic hot water (DHW). This must be raised to a much higher temperature (at least 60°C) in order to avoid problems from legionella. Initially there were plans to achieve this by means of a centralised combined heat and power (CHP) engine, but it was felt it would be more effective to heat the DHW on an individual building basis. The load profile of the health care centre (not connected to the mine water system) was individually suited to the application of CHP, but that of the residential buildings was not so these were instead equipped with individual gas-fired condensing boilers. The design principles for the buildings that have minimised their energy demand also means there is a significant amount of time when the buildings require neither heating nor cooling. Overall the energy demand for the redeveloped areas is quite small. This conflicts with the overall need to recover money invested by means of energy sales unless the cost levied per unit of energy is very high. This dilemma faces all new developments where a very good environmental performance is being achieved through a 16 combination of minimising demand and expensive low carbon technologies to produce a diminished supply. The overall system will be controlled by an intelligent energy management system including telemetering of the energy uses/flows at the end-users. 3.1.9 Minimising demand: Low Exergy and Building Design As with many of the renewable energy systems that are now being implemented more rapidly than ever before, the use of the mine water energy is limited by the nature of the resource itself. However, if we are able to make use of available renewable energy resources, we can conserve fossil fuels for situations where there is no alternative. In the vicinity of Heerlen the highest temperature mine water that can be readily accessed is 32°C. The use of water at this temperature requires a specialised approach. Specifically, it calls for an attempt to match as well as possible the energy demand to the available supply. High grade fuels such as fossil fuels and, even more so, electricity are extremely versatile and concentrated. They can be converted to many other energy types for an enormous range of mechanical purposes and industrial processes requiring 100s of degrees. It is not therefore thermodynamically smart to use such fuels for temperature elevations of several 10s of degrees. Conversely water at 32°C is not at all flexible in its range of useful applications. As an energy resource it is very low grade. Yet even as a preheat for a conventional heating system where water is heated from 10°C to 80°C, it could potentially contribute 30% of the required temperature rise. This enables fossil fuel use to be reduced with consequent conservation of valuable resources for
applications where there is no alternative, and reduces the associated carbon emissions. If we then design the building and heating equipment to be capable of using water at much lower temperatures then the potential saving increases. The scientific name that is used to define grade or quality of energy is ‘exergy’. Building design aspects: • Low ventilation rate • High insulation • Thermal storage and or mass System aspects: • Focus on underfloor, wall and ceiling heating, with even distribution of heating surface. 3.1.10 Customers of the Heerlen Mine Water Scheme The first customer is the Housing Association Weller specifically through the regeneration scheme at Heerlerheide Centre. Further schemes (Table 3.4) will come on line in due course, with the Heerlen APG head office scheme connecting imminently. The pipes have been designed to cater for the extra mine water flows that will be needed when the clients that are anticipated connect to the network. Heerlerheide Centre The regeneration of Heerlerheide Centre includes new build residential (330 dwellings), commercial (floor area 3,800 m 2) and public (16,200 m 2) buildings, including new health care and educational facilities. The first new building and construction activities in Heerlerheide Centre started in 2006 and will be completed by 2011. Most of all the buildings that are planned as part of this development will be connected to the mine water heating and cooling networks. They will all be confined to a very compact area so that the length of the energy distribution pipes is minimised. The principal stakeholder in the Heerlerheide development is the Housing Association Weller. This scheme and the role of Weller in delivering it is described further in the case study later on in this Guide. Heerlen APG head office This development involves the improvement of a large existing building, the APG head office of floor area 60,000 m 2. The total building envelope has been refurbished to a level better then the current Dutch Building Decree requirements for new buildings. The mine water will be used for providing both heating and cooling. The building will be designed so that low temperature heating and high temperature cooling can be used for all the offices. The APG building will have a direct connection to the mine water wells and will have its own energy station that will be equipped with heat pumps to ensure the office temperature stays within the required range. The glazing system will be designed with low transmissivity in order to limit solar radiation in summer; this makes it possible to use high temperature cooling, most of the time directly from mine water. Projected demands (heat and cold) from these and other future customers are summarised in Table 3.4. Table 3.4: Total demand for mine energy from water per hour and per year (data from September 2008) Customers current & potential future 3.1.11 Conclusion Abandoned and flooded mines can be reused for a new sustainable energy supply for heating and cooling of buildings. The Minewater Project in Heerlen shows that the temperature (about 30°C) found at 700m and the temperature of the shallow wells (16° – 18°C at 250m) can potentially make a significant contribution to the heating and cooling requirements of buildings provided they are very well insulated, have energy efficient ventilation systems and have systems designed to use moderate temperatures like underfloor / wall heating. However, the systems are not without their problems, since it is difficult to exactly predict in advance what the temperature and volume flows will be. This is because one commonly does not know precisely which parts of the mine (infrastructure) are still open and which are not. For the Heerlen pilot this meant nothing less than changing the whole original purely geothermal philosophy of the system. Instead of direct provision of warm water, the warm reservoir is used for a combination of large scale cold / heat storage in addition to the geothermal supply. 3.2 The proposed Midlothian pilot The shaft of the disused Monktonhall Colliery is near the proposed centre of Shawfair. This shaft could be used to access a resource of warm water for driving a heat pump to provide heating to a district heating network. The technical viability of any geothermal energy source depends on satisfying three criteria: • • • Floor area in m 2(GFA) Maximum delivery m 3/h (= hour) Is the water source hot enough to provide useful energy? Is there sufficient water available for the life of the project? Can the water be abstracted at a sufficient rate to provide the net power required by the project? Preliminary studies indicated that these 3 criteria are satisfied. Hot water Cold water Volume m 3/year Maximum delivery m 3/h (= hour) Volume m 3/year EC Heerlerheide 48 144,000 86 215,000 APG 41,000 26 66,000 241 845,000 SON, CBS new 22,000 28 70,000 19 68,000 SON, CBS old 43,500 65 163,000 126 441,500 Total: 167 443,000 472 1,569,500 NB: CBS will probably be connected to the mine water system Technical aspects of the Minewater Pilots 17
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Page 3 and 4: Contents Foreword v 01 Overview 1 1
Page 5 and 6: Foreword This information guide is
Page 7 and 8: 01 Overview Abandoned and flooded m
Page 9 and 10: 02 Pre-investment studies: determin
Page 11 and 12: Hydraulic, physical and chemical me
Page 13 and 14: Fig 2.4: Lorraine ore fields (Yello
Page 15 and 16: 03 There are two basic options for
Page 17 and 18: Technical aspects of the Minewater
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Page 25 and 26: The size of the Shawfair developmen
Page 27 and 28: 04 Economic and organisational issu
Page 29: Fig 4.2: Proposed Business Model Mi
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