cooling applications such as desalination , refrigeration and even the production of electricity . The paper concludes , however , that the best economic value is achieved when recovered heat at a temperature of about 70 ° C is used for space heating purposes .
This directly exposes one of the major issues around data centre heat reuse at the moment . Servers generally remove their heat using air . Currently , in the best case this heat is rejected at a temperature of about 35- 40 ° C . Generally , it is lower . Depending on the heat collection effectiveness , this temperature quickly drops to 28 ° C before the heat is captured in a system that can transport it to the user . Water cooled servers will eliminate this problem . But these are still at least five years away from becoming mainstream and have been so for the past 15 years . This article therefore only considers air cooled servers .
Nevertheless , more recently , several operational systems have been realised in The Netherlands . In particular , campus settings with a large share of the building population being new builds are interesting . These often utilise low temperature heating technologies , where data centres in combination with underground aquifer cold and warmth storage can be a real asset to the campus . Similarly , at a different campus a data centre has been connected to a dis-balanced warmth and cold ring . With the connected buildings asking for more heat than is available , and producing more cold than is required , these data centres were a welcome connection onto this ring . The common theme in these success stories is the cooperation with a campus .
This being said , the theme of energy reuse is also ‘ out of the box ’ thinking . For smaller data centres there are opportunities : offices can be both heated and cooled by making smart use of the data centre heat removal system .
What if you do not yet have a heat reuse customer , but want to prepare for one ? Your best bet may be on installing a chilled water system , which for only a little extra investment can be equipped with a heat exchanger for realising heat harvest and reuse .
To summarise the above : the challenge for heat reuse is either to find nearby users that can make good use of the available heat , or to transfer the low grade thermal energy ( warm air and warm water ) into high grade thermal energy that has a larger audience of possible consumers . The latter may require additional investments , for instance for additional heat pumps , and the business case therefore could require guaranteed customers with dedicated contracts .
What could happen next ? And now new and exciting possible collaborations are visible on the horizon . The Dutch glass house agriculture industry , a large consumer of heat and power , is uniting to investigate the feasibility of putting excess data centre heat to good use . This is an industry which is accustomed to large scale cooperation in energy projects and park development .
However , while 80 per cent of the operational expenditures of glass house greeneries is energy related , it is not necessarily a given that external heat supply is required . It depends on the crops grown . These generally fall into two categories , lit or unlit . Lit crops demand large quantities of electricity , which is currently most efficiently produced using cogeneration facilities that at the same time provide the required heat . But the non-lit crops still require heat , and green house farmers too are working on reducing the use of fossil fuels . Therefore , within a park development with several growers there will always be a substantial base load that can be supported by data centre facilities . Upgrading the available data centre heat by means of heat pumps will be required , as the ideal temperature of the heating medium in green houses is 63 ° C . When working towards realising the necessary facilities , a data centre / green house collaboration can draw on the extensive cooperating experience of the green house industry .
So maybe , in a few years ’ time the tasty salad you serve for dinner might have been grown from the heat produced by your Facebook and WhatsApp activities .
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