Manure Handling
Digester and bio gas handling
Manure Biogas Steam Power Data center Dairy Farm Figure 2: Flow chart of material and energy flow in the facility. The theories
Researchers argue that data centres have natural symbiosis with dairy farms and animal feeding operations. In their hypothetical case study, they show that a 10,000-cow dairy farm with an average daily manure production of 547 metric tons can power a 1MW data centre when the centre’s cooling system is exploited to aid the AD process. Waste heat from power generation systems is used to maintain digester temperature at 40°C. This is achieved by the injection of steam generated from the hot exhaust of the power generation system. Indeed, waste heat from the data centre IT equipment is also well matched for use in the digester. Biogas is produced in the digester
A 1100kW
at a temperature of 40°C. This needs to be cleaned to prevent corrosion and damage of power generation equipment. Methane accounts for 60 to 70% of the biogas produced, amounting to an annual production of 6.4 million cubic metres. The power generation system comprises of a low- BTU gas-fired lean-burn reciprocating engine driven generator set. With an electrical efficiency of 37%, the generator provides power for the IT equipment and air handling units in the data centre and refrigeration equipment on the farm. Based on design methane production, the system can generate over 10.8 GWh annually. This implies that a total demand of 1.2MW can be supported without grid power.
F Utility PCC
www.netcommseurope.com
LP Saturated Steam 130C
Biogas 400 MMSCF 60% Methane
Data Centre
Apart from the data centre demand, onsite generation can support electrical demand on the farm. Waste heat from engine exhaust can be used to generate low pressure steam for steam injection and hot water needs. Engine jacket cooling water can be used to produce 90°C hot water for the data centre cooling system using conventional silica gel-water adsorption refrigeration cycle. It is assumed that only 70% of the available waste heat can be extracted due to heat transfer losses. The available waste heat from the power generation system is estimated at 17 GJ/hr. Waste heat-driven adsorption cooling systems can cool data centre equipment and satisfy the refrigeration demand of the dairy farm. The hot water demand for data centre cooling is 4.5 MMBTU/hr while that for dairy cooling is 0.5 MMBTU/hr. The total waste heat potential of the generation system is 16 MMBTU/ hr (~17GJ/hr). Overall, the total hot water demand for cooling system is 40% of available waste heat potential. The balance waste heat, mostly in the form of low pressure steam, is used for maintaining optimum temperature (40°C) in the digester and for process heating in the farm. Assuming each cow produces 55kg of manure per day and the digester charge needs to be heated by 30°C (above ambient), the steam requirement in the digester is estimated at 0.33kg/s.
B
Exhaust 400
°C
Boiler H
C Chilled Water Return Process Steam
HotWater 80°C
Chilled Water Supply D Conclusion
Flash Chamber
°C
The report also explains that this set-up presents considerable potential economic benefits for both farmer and data centre manager. Contemporary data centres are increasingly co-located with power generation and/or cooling resources in order to reduce operating costs. The existence of large dairy and animal feeding operations presents a co-location opportunity, one where the heat output from the data centre can be used to develop synergy with its energy source. Researchers assert that farmers can be assured of considerable sustained demand from data centres, with their substantial, continuous and long-term power needs, and through a power purchase agreement, this could be quite profitable from a farmer’s perspective. The potential for carbon offsets through reduction of methane emissions could also translate into a cost saving. Data centre managers benefit from the sustained, relatively low-cost source of power, and through reduction in their own carbon footprint. As well as providing an effective
200 °C
Exhaust gas
Make Up water (30°C)
Hot Water 105
E
1200gpm 1025gpm
Farm Facility G
mechanism for managing farm waste, controlling odours and reducing greenhouse gas emissions, anaerobic digestion could provide an attractive solution to the problem of powering data centres in addition to providing a fuel source for power generation.
Power Generation
Cooling Infrastructure Hot water Heat
Based on research by Ratnesh Sharma, Tom Christian, Martin Arlitt, Cullen Bash and Chandrakant Patel, Hewlett- Packard Laboratories
NETCOMMS europe Volume I, Issue 4 2011 43
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