image OCEAN ENERGY.
Marine turbine designs look somewhat like wind turbines but they must contend with reversing flows, cavitation and harsh underwater marine conditions (e.g. salt water corrosion, debris, fouling, etc). Axial flow turbines must be able to respond to reversing flow directions, while cross-flow turbines continue to operate regardless of current flow direction. Rotor shrouds (also known as cowlings or ducts) can enhance hydrodynamic performance by increasing the speed of water through the rotor and reducing losses at the tips. Some technologies in the conceptual stage of development are based on reciprocating devices incorporating hydrofoils or tidal sails. Two prototype oscillating devices have been trialled at open sea locations in the UK.117 The development of the tidal current resource will require multiple machines deployed in a similar fashion to a wind farm, and siting will need to take into account wake effects.118
Renewable heating and cooling has a long tradition in human culture. Heat can come from the sun (solar thermal), the earth (geothermal), ambient heat and plant matter (biomass). Using solar heat for drying processes and or wood stoves for cooking have been done for so long that they labeled “traditional”, but today’s technologies are far from old-fashioned. Over the last decade there have been improvements to a range of traditional applications many of which are already economical competitive with fossil-fuel based technologies or starting to be. This chapter presents the current range of renewable heating and cooling technologies and gives a short outlook of the most sophisticated technologies, integrating multiple suppliers and users in heat networks or even across various renewable energy sources in integrated heating and cooling systems. Some of the emerging areas for this technology are building heating and cooling and industrial process heat. Solar Thermal Technologies
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Solar thermal energy has been used for the production of heat for centuries but has become more popular and developed commercially for the last thirty years. Solar thermal collecting systems are based on a centuries-old principle: the sun heats up water contained in a dark vessel. The technologies on the market now are efficient and highly reliable, providing energy for a wide range of applications in domestic and commercial buildings, swimming pools, for industrial process heat, in cooling and the desalination for drinking water. Although mature products exist to provide domestic hot water and space heating using solar energy, in most countries they are not yet the norm. A big step towards an Energy [R]evolution is integrating solar thermal technologies into buildings at the design stage or when the heating (and cooling) system is being replaced, lowering the installation cost. Swimming pool heating: Pools can make simple use of free
source IPCC 2012: SPECIAL REPORT ON RENEWABLE ENERGY SOURCES AND CLIMATE CHANGE MITIGATION. PREPARED BY WORKING GROUP III OF THE INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE, CAMBRIDGE UNIVERSITY PRESS.
references 117 118 119 120 121
heating, using unglazed water collectors. They are mostly made of plastic, have no insulation and reach temperatures just a few degrees above ambient temperature. Collectors used for heating swimming pools and are either installed on the ground or on a nearby rooftop and they word by pumping swimming pool water through the collector directly. The size of such a system depends on the size of the pool as well as the seasons in which the pool is used. The collector area needed is about 50 % to 70 % of the pool surface. The average size of an unglazed water collector system installed in Europe is about 200 m2.121 Domestic hot water systems: The major application of solar thermal heating so far is for domestic hot water systems. Depending on the conditions and the system’s configuration, most of a building’s hot water requirements can be provided by solar energy. Larger systems can additionally cover a substantial part of the energy needed for space heating. Two major collector types are:
ENGINEERING BUSINESS, 2003; TSB, 2010. PEYRARD ET AL. 2006. VANZWIETEN ET AL., 2005. VENEZIA AND HOLT, 1995; RAYE, 2001; VANZWIETEN ET AL., 2005. WEISS ET AL. 2011.
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RENEWABLE ENERGY TECHNOLOGIES
figure 9.22: vertical axis device
9.3.8 renewable heating and cooling technologies
energy technologies |
Capturing the energy of open-ocean current systems is likely to require the same basic technology as for tidal flows but with some different infrastructure. Deep-water applications may requre neutrally buoyant turbine/generator modules with mooring lines and anchor systems or they could be attached to other structures, such as offshore platforms.119 These modules will also have hydrodynamic lifting designs to allow optimal and flexible vertical positioning.120 Systems to capture energy from open ocean current systems may have larger rotors, as there is no restriction based on the channel size.
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© STEVE MORGAN/GP
image THE PELAMIS WAVE POWER MACHINE IN ORKNEY - ALONGSIDE IN LYNESS THE MACHINE IS THE P2 . THE PELAMIS ABSORBS THE ENERGY OF OCEAN WAVES AND CONVERTS IT INTO ELECTRICITY. ALL GENERATION SYSTEMS ARE SEALED AND DRY INSIDE THE MACHINES AND POWER IS TRANSMITTED TO SHORE USING STANDARD SUBSEA CABLES AND EQUIPMENT.