Monthly Archives: August 2010

Electricity from ocean water

Generating energy from ocean waters.  According to  Hawaiian researchers  the Leeward side of Hawaii  may be ideal for future ocean-based renewable  energy plants,  that would use seawater from the oceans’ depths to drive massive heat engines and produce  steady  amounts of renewable energy.

The technology involves placing a heat engine between warm water collected at the ocean’s surface and cold water pumped from the deep ocean. Like a ball rolling downhill heat flows from the warm reservoir to the cool. The greater the temperature difference, the stronger the flow of heat that can be used to do useful work such as spinning a  turbine and generating electricity.

The technology of Ocean Thermal Energy Conversion (OTEC) dates back more than a half century.  However, it has never taken off, largely because of the relatively low cost of oil and other fossil fuels.  But if there are any places on Earth where large OTEC  facilities would be cost competitive,  it  is where the ocean temperature differentials are the greatest.

Harness summer heat for use cold winters

A Swiss university has come up with an ambitious plan to save tons of power every year on through heating and air conditioning systems. Höggenberg Campus in Switzerland is building a new phase of the school called Science City where warm air will be stored in the summer to be used for heating in the winter.

Every summer, appliances, computer servers, and people themselves give off a lot of heat. In most cases, this heat is pumped out into the environment through fans and cooling devices, essentially wasting a natural power source. Through an innovated plan developed by Gehrard Schmitt, old vice president of Planning and Logistics back in 2006, Science City will harness that natural heat, pump it underground, and store it during the summer. Then, when temperatures drop during the winter months, that warm air will be pushed back up into buildings where it will act as a heating system.

Until now most of the waste heat from appliances and people was released into the surrounding air, thus being lost to further use. In future it will be stored in the ground via ground storage probes operating like a large heat-exchanger. Via circulating water system, the waste heat is put into storage in the cool ground, whose temperature ranges from 8 to 18°C. In winter the heat is pumped up again through the same circulation system and used to heat the building. Since the temperature range of 8 to 18°C is insufficient for this, the heat is “upgraded” to 30 to 35°C using several electrically-driven heat pumps. The system is decentralised: each building is equipped with a computer that controls precisely how much heat is needed to heat it.

Heat can be tapped off via the water circulation system from each of the storage units, nine of which will be installed by 2020. The potential is enormous: although the ground’s heat capacity, around 1.0 kJ/kgK, is about one quarter of that of water, the gigantic volume of the ground storage compensates for this disadvantage. The engineers want to make four million cubic metres of ground usable on the Hönggerberg Campus. A density of 2500 kilograms per cubic metre and a 5 Kelvin temperature difference between charging and discharging yields a total capacity of 13 to 15 gigawatt-hours, corresponding to the energy content of around 1500 tons of petroleum.

Schmitt’s revolutionary heating and cooling system uses low-energy, or “anergy.” However the system must prove itself first. There are, as yet, no reference projects. Once completed in 2020, Science City will only need to rely on traditional electricity for one-twelfth of its heating and cooling needs. The rest of the energy will be provided through Schmitt’s heat-exchanger system. If it all goes according to plan Science City will be almost CO2-free by 2020.