heat can be transferred directly to the lake water heat sink. This is referred to as "free cooling", but is not actually free, since pumps and fans run to circulate the lake water and building air. One added attraction of deep lake water cooling is that it saves energy during peak load times, such as summer afternoons, when a sizable amount of the total electrical grid load is air conditioning. Advantages Deep water source cooling is very energy efficient, requiring only 1/10 of the average energy required by conventional cooler systems. Consequently, its running costs can also be expected to be much lower. The energy source is very local and fully renewable, provided that the water and heat rejected into the environment (often the same lake or a nearby river) does not disturb the natural cycles. It does not use any ozone depleting refrigerant. Depending on the building's cooling demand, and local weather, deep water source cooling can often satisfy a complete portion of a building's cooling demand, eradicating a building's reliance on mechanical refrigeration provided through a chiller. This not only reduces the building's electrical demand (or steam demand for applications using absorption refrigeration), but also curtails dependency on evaporative cooling towers which can often times harbor the fatal bacterium Legionella pneumophila. However, building operators must adhere to, and practice correct disinfection procedures before restarting any cooling towers which remained dormant during cooler days when deep water source cooling was able to meet the building's cooling demand. Depending on the needs and on the water temperature, couple heating and cooling can be considered. For example, heat could first be extracted from the water (making it colder); and, secondly, that same water could cycle to a refrigerating unit to be used for even more effective cold production. Disadvantages Deep water source cooling requires a large and deep water quantity in the surroundings. To obtain water in the 3 to 6 °C (37 to 43 °F) range, a depth of to is generally required, depending on the local conditions. The set-up of a system is expensive and labour-intensive. The system also requires a great amount of source material for its construction and placement. Although deep water source cooling is referred to as "free cooling" in some literatures, a considerable amount of energy (typically electrical) is expended to operate pumps with a sufficient head to overcome frictional, and minor losses in distribution