Green Dictionary

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sineQN’s green dictionary is a quick reference tool. The chosen words and definitions are updated in response to the evolving nature of environmental issues and initiatives.

CURRENT TOP FIVE TERMS

1. COMBINED HEAT & POWER (CHP)

The simultaneous generation of usable heat and power (usually electricity) in a single process. CHP is a highly efficient way to use both fossil and renewable fuels and can therefore make a significant contribution to the UK’s sustainable energy goals, bringing environmental, economic, social and energy security benefits.

2. FREE COOLING

Free cooling uses the cooling capacity of low external air temperatures to assist in the process of chilling water or directly cool a space . External air at around 7-14 Deg C can be used to meet a cooling load and thus reduce the energy consumed by the mechanical refrigerant plant. Free cooling systems take advantage of these favorable weather conditions to enable chiller plant to be shut down for long periods, saving significant amounts of energy and cutting carbon emissions.

3. WASTE TO ENERGY

Waste to energy conversion is an increasingly recognised approach to resolving two issues in one – waste management and sustainable energy. Waste represents an increasingly important fuel source. Using waste as fuel can have important environmental benefits. It can not only provide a safe and cost-effective way of waste disposal but can also help reduce carbon dioxide emissions. Whilst energy can be derived from waste by burning landfill gas, there are also alternative methods to generate energy from waste. When waste is incinerated in large amounts, the heat energy can be recycled and used to heat factories, hospitals and other large buildings. Alternatively, the heat can be used to generate electricity. This is done by using the steam created by combustion to drive a steam turbine. Electricity generating waste plants can typically process between 20,000 and 600,000 tonnes of waste per year, from which they can generate between 1 and 40 MW of electricity. Waste-derived fuel can also be burnt in boilers as an alternative to coal. Any energy that is recovered from biological waste can be regarded as renewable. It comes from plant material – either directly, or in the case of animal waste, paper or card, indirectly. As plants grow they absorb carbon dioxide from the atmosphere. When biomass is used as fuel, this carbon dioxide is returned to the atmosphere, making the process carbon neutral.

4. HOT & COLD AISLE CONTAINMENT

Containment of hot/cold aisles and ducting hot air from cabinets are intended to prevent cool/exhaust air mixing within data halls or server rooms. Generally rows of cabinets face each other so that cool air can reach the equipment air intakes at the required set point temperature for the room.

A cold-aisle containment system (CACS) encloses the cold aisle, allowing the rest of the data hall to become a large hot-air return plenum. By containing the cold aisle, the hot and cold air streams are separated. This containment method requires that the rows of racks be set up in a consistent hot-aisle / cold-aisle arrangement. A hot-aisle containment system (HACS) encloses the hot aisle to collect the IT equipment’s hot exhaust air, allowing the rest of the room to become a large cold-air supply plenum.

Both hot-aisle and cold-aisle containment provide significant energy savings over traditional uncontained configurations.

5. RACK HYGIENE

Rack Hygiene is a newly coined term used to describe the care in which an IT server rack envelope should be designed, controlled and maintained. The rack envelope consists of the entire volume of space from the floor to top of the rack itself. The use of blanking plates and other fittings around the edge, top, floor, or the rack direct air intake so that only air from the cold aisle reaches equipment intakes and prevent leakage of exhaust air into the intake area. Fans on the top or rear doors of the cabinet ensure a negative pressure for exhaust air coming out of equipment. This effective airflow management prevents hot spots, which are especially common in the top spaces of a rack, and allows the temperature of cold aisles to be raised and thus produce energy savings. Furthermore,ineffective rack airflow management at the rack and row level is a key contributor to aisle and room overheating.