CASE STUDY
Using Digested Farm Waste to Power a Data Centre Where There’s Muck... By Neil O’Sullivan
At its labs in California, HP has been exploring the possibilities of combining the energy potential of digested farm waste with the power requirements of a data centre. Although the information technology and livestock industries may seem completely disjointed, they have complementary characteristics that can be exploited for mutual benefit.
In a recently published paper, researchers have put together a hypothetical case study to demonstrate not only that the use of farm-waste- driven power supplies in data centre management is possible, but that it may be economically advantageous to both data centre managers and farmers.
The background
The rapid growth in demand for complex, resource-intensive IT infrastructures is exhausting data centre capacity, and putting increased pressure on power supplies. Data centres draw power from the utility grid, and often also use onsite generation. Onsite generation is commonly performed using diesel generators as backup sources. Uninterruptible Power Supplies (UPS) condition power derived from utility grid and from the generation sources and store it for emergency use. Data centres also incorporate a cooling system comprised of computer room air conditioning (CRAC) units, primary and secondary pumps, chillers, and cooling towers. The concentration of IT equipment
within the data centre poses several challenges. First, the power density can be quite significant, making it difficult to obtain sufficient electricity from the utility grid. Heavy power consumption, if from a non-renewable source, can also make a company liable for economic penalties regarding operational carbon footprint. Onsite generation from renewable resources is therefore attractive. Data centres also generate a lot of
waste heat, and cooling infrastructures increase the centre’s power usage significantly. This has motivated movement towards economisation, like the use of outside air to directly cool a data centre, and high temperature computing. This could lower both the capital and operational costs of cooling, and improve the quality of the waste heat by increasing its temperature. Bearing these considerations in
mind, researchers turned their minds to the livestock industry. Like the IT sector, this industry has recently been required to concentrate its operations in order to meet increased demand. It
42 NETCOMMS Volume I, Issue 4 2011
also has an imperative to reduce the pollution generated by livestock waste. As a result, manure management systems that enable pollution prevention and produce energy are becoming increasingly attractive. Power can be generated from manure
Manure Handling
Digester and bio gas handling
Manure
in two ways. It can be burned, and the resultant heat can produce steam to power turbines in the traditional way. This method, however, brings with it all the problems of harmful emissions. The alternative method uses the anaerobic digestion (AD) process to produce a biogas containing about 60-70% methane. This method retains
A
LP Saturated Steam 130C
Biogas 400 MMSCF 60% Methane
Exhaust 400
°C
Boiler H
1100kW Data Centre F Utility PCC Figure 1: Process flow diagram for biogas energy generation.
A detailed process flow diagram is shown above. Clean biogas generated in the digester facility, (A) is piped to the gas generator set. The generator provides power to the data centre power distribution system through a system of UPS and power distribution units. Waste heat from the engine cooling jacket is used to heat hot water in the primary heat recovery unit (B). Additionally, heat from the engine exhaust is recovered in the secondary heat recovery unit (C) to further heat the hot water beyond 100°C. The flash chamber (D) allows generation of steam and hot water for different site needs. Pressure in the flash chamber is controlled to alter the rate of steam generation. Steam is used for heating the digester and other heating needs in the farm (G). Hot water from the flash chamber is used in the desorber of the adsorption cooling system (E). It is mixed with make-up water to account for the loss due to steam discharge. Chilled water from the adsorption system is fed into the site cooling system which serves the data centre and the farm. A primary-secondary loop can be added if needed. Control valves can divert water to the data centre (F) based on demand. With change in farm and data centre demand, biogas can be diverted to the boiler (H) to generate steam for hot water needs, thus reducing power generation. Such decisions can also be made based on maintenance schedules and operating cost. Multiple smaller units can be installed to manage generator downtime with additional power draw from the grid. Based on availability, natural gas or biogas will be used to fire boilers to provide steam and hot water for cooling and heating needs.
8 C Chilled Water Return Process Steam
Farm Facility G
HotWater 80°C
Chilled Water Supply B D Biogas Steam Power Data center
the inorganic materials in the manure (such as nitrogen, phosphorus and potassium) for reuse as fertiliser while the organics are broken down in a four stage process to yield methane and carbon dioxide. The methane can be used for heating, cooling or to produce power, which can be generated using lean- burn reciprocating engines available at capacities up to a few MW. The average dairy cow produces 54.7 kilograms of manure per day, approximately 20 metric tons per year. Using this method, the manure produced by one dairy cow in a day can generate 3.0 kWh of electrical energy.
Power Generation Cooling Infrastructure Hot water Heat Dairy Farm 200 °C
Flash Chamber
Hot Water 105
°C E
1200gpm 1025gpm
Exhaust gas
Make Up water (30°C)
Copyright © 2010 by ASM
www.netcommseurope.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60