Alternative Sources of Energy at Race Rocks

Starting in 1997, Lester B. Pearson College had to raise the funds to keep the diesel generators working to supply electricity to Race Rocks . The cost of doing this was originally $11,000 per year and within 4 years reached $20,000. The lighthouse light and foghorn had been made energy self- sufficient with 8 solar panels and a battery array installed by the Coast Guard by 1997. By 1998 proposals to develop support for alternate energy technologies to make the rest of the island energy-self sufficient were underway.

In September 2006, a bi-directional flow turbine was installed at a depth of 20m below the water surface at Race Rocks. There has been a trend in investigating and implementing new, greener sources of energy at Race Rocks, and this is the next step in that process.

Ocean thermal energy conversion (OTEC ) uses the temperature difference that exists between deep and shallow waters to run a heat engine. As with any heat engine, the greatest efficiency and power is produced with the largest temperature difference. Historically, the main technical challenge of OTEC was to generate significant amounts of power efficiently from this very small temperature ratio. Changes in efficiency of heat exchange in modern designs allow performance approaching the theoretical maximum efficiency.

The Earth's oceans are continually heated by the sun and cover nearly 70% of the Earth's surface; this temperature difference contains a vast amount of solar energy, which can potentially be harnessed for human use. If this extraction could be made cost effective on a large scale, it could provide a source of renewable energy needed to deal with energy shortages and other energy problems. The total energy available is one or two orders of magnitude higher than other ocean energy options such as wave power; but the small magnitude of the temperature difference makes energy extraction comparatively difficult and expensive, due to low thermal efficiency. The energy carrier, seawater, is free, though it has an access cost associated with the pumping materials and pump energy costs. However OTEC plants tend to operate at a low overall efficiency thus any thorough cost-benefit analysis should include these factors to provide an accurate assessment of performance, efficiency, operational, construction costs, and returns on investment.

Aquaculture is the most well-known by-product of OTEC. It is widely considered to be one of the most important ways to reduce the financial and energy costs of pumping large volumes of water from the deep ocean. Deep ocean water contains high concentrations of essential nutrients that are depleted in surface waters due to biological consumption. This "artificial upwelling" mimics the natural upwellings that are responsible for fertilizing and supporting the world's largest marine ecosystems, and the largest densities of life on the planet.

Cold-water delicacies, such as salmon and lobster, thrive in the nutrient-rich, deep, seawater from the OTEC process. Microalgae such as Spirulina, a health food supplement, also can be cultivated in the nutrient rich water. Because the OTEC process uses cold, deep-ocean water and warm ocean water from the surface, it can be combined in various ratios to deliver sea water of a specific temperature conducive to maintaining an optimal environment for aquaculture.

Wave Power

Wave power is the transport of energy by ocean surface waves, and the capture of that energy to do useful work — for example for electricity generation, water desalination, or the pumping of water (into reservoirs).

Wave power devices are generally categorized by the method used to capture the energy of the waves. They can also be categorized by location and power take-off system. Method types are point absorber or buoy; surfacing following or attenuator oriented parallel to the direction of wave propagation; terminator, oriented perpendicular to the direction of wave propagation; oscillating water column; and overtopping. Locations are shoreline, near shore and offshore. Types of power take-off include: hydraulic ram, elastomeric hose pump, pump-to-shore, hydroelectric turbine, air turbine, and linear electrical generator. These capture systems use the rise and fall motion of waves to capture energy. Once the wave energy is captured at a wave source, power must be carried to the point of use or to a connection to the electrical grid by transmission power cables.

Here is a description of a wave power system:

An example of a surface following device is the Pelamis Wave Energy Converter. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity. The Pelamis is an attenuating wave energy converter designed with survivability at the fore. The Pelamis's long thin shape means it is almost invisible to hydrodynamic forces, namely inertia, drag, and slamming, which in large waves give rise to large loads. Its novel joint configuration is used to induce a tunable cross-coupled resonant response. Control of the restraint applied to the joints allows this resonant response to be ‘turned-up’ in small seas where capture efficiency must be maximised or ‘turned-down’ to limit loads and motions in survival conditions.

The Pelamis device consists of a series of semi-submerged cylindrical sections linked by hinged joints. The wave-induced relative motion of these sections is resisted by hydraulic cylinders which pump high pressure oil through hydraulic motors via smoothing hydraulic accumulators. The hydraulic motors drive electrical generators to produce electricity. Power from all the joints is fed down a single umbilical cable to a junction on the sea bed. Several devices can be connected together and linked to shore through a single seabed cab

Deep water wave power resources are truly enormous, between 1 TW and 10 TW, but it is not practical to capture all of this. The useful worldwide resource has been estimated to be greater than 2 TW. Locations with the most potential for wave power include the western seaboard of Europe, the northern coast of the UK, and the Pacific coastlines of North and South America, Southern Africa, Australia, and New Zealand. The north and south temperate zones have the best sites for capturing wave power. The prevailing westerlies in these zones blow strongest in winter. Waves are very predictable. The waves that are caused by winds can be predicted five days in advance. Tidal currents, caused by lunar positions, are known 100 years in advance. Water has a power density that is 832 times greater than air's power density. That means that large amounts of energy can be obtained from relatively small devices. For example, it would require a wind turbine three times its size to generate the same amount of power as a regular-sized underwater turbine.

Challenges

The device has to efficiently convert wave motion into electricity. Generally speaking, wave power is available at low speed and high force, and the motion of forces is not in a single direction. Most readily-available electric generators operate at higher speeds, and most readily-available turbines require a constant, steady flow.

There is a potential impact on the marine environment. Noise pollution, for example, could have negative impact if not monitored, although the noise and visible impact of each design varies greatly.