WAVE ENERGY AS A POTENTIAL RENEWABLE ENERGY RESOURCE

At present most of the energy needs are met through fossil fuels & oil. Therefore developing countries are dependent on oil imports for their energy needs. At present there are about two billion people without access to electricity. Therefore there is an urgent need all over world to tap renewable energy sources. Total renewable energy sources account for 56 EJ of energy, almost 14% of the total world energy i.e. 401 EJ.

Wave energy

Waves in sea are generated by the action of winds blowing over water and can be used as a renewable source of energy. In fact sea could be viewed as a vast collector of energy transferred by wind over large sea. Surface and stored as wave energy. Wave energy potential varies from place to place depending upon its geographic location. Two factors affecting the magnitude of wave energy are wind strength & uninterrupted distance over the sea that the wind can blow.

 

Potential

The total wave power potential of the world is 2 x 10⁶ MW. The tidal energy is wavering with 250 Kw available from December to March, 75 Kw between April to November and has peak value of 150 Kw. The economics of wave energy power, though not yet competitive with fossil fuels, are promising and the situation is improving with more advanced technology. Capital costs for 100 MW installation is $1200 to $1500/Kw with operating costs of 5 cents / Kwh & load factor around 20%. Estimated international cost for power from wave energy is around 9.2 C/KwH.

 

Current Status

The first commercial wave plant in the world, Limpet 500, was installed on the island of Islay, Scotland, in 2000 and has been providing power to the grid for U.K. The Limpet 500 is a 0.5 MW capacity plant for sitting on exposed shores, utilizing an oscillating column. design. In India 150 KW system is set at Thiruvananthpuram. The United Kingdom is said to be the dominant player in wave power with a forecast capacity of 14.7 MW. Portugal, Spain and Denmark are other significant markets but lag far behind U.K.

TIDAL ENERGY – LATEST DEVELOPMENT

The oldest technology to harness tidal power for the generation of electricity involves building a dam, known as a barrage, across a bay or estuary that has large differences in elevation between high and low tides. Water retained behind a dam at high tide generates a power head sufficient to generate electricity as the tide ebbs and water released from within the dam turns conventional turbines. Though the American and Canadian governments considered constructing ocean dams to harness the power of the Atlantic tides in the 1930s, the first commercial scale tidal generating barrage rated at 240 MW was built in La Rance. This plant continues to operate today as does a smaller plant constructed in 1984 with the Annapolis Royal Tidal Generating Station in Nova Scotia, rated at 20 megawatts (enough power for 4,500 homes). Other tidal generating station operating today, is located near Murmansk on the White Sea in Russia, rated at 0.5 megawatts.

 

These first-generation tidal power plants have all withstood the rigours of the marine

environment and been in continuous pollution-free operation for many years. But due to the very high cost of building an ocean dam to harness tidal power, and environmental problems from the accumulation of silt within the catchment area of the dam (which requires regular, expensive dredging), engineers no longer consider barrage-style tidal power feasible for energy generation.

 

Engineers have recently created two new kinds of devices to harness the energy of tidal currents (AKA ‘tidal streams’) and generate renewable, pollution-free electricity. These new devices may be distinguished as Vertical-axis and Horizontal axis models, determined by the orientation of a subsea, rotating shaft that turns a gearbox linked to a turbine with the help of large, slow-moving rotor blades. Both models can be considered a kind of underwater windmill. While horizontal-axis turbine prototypes are now being tested in northern Europe (the UK and Norway). A vertical-axis turbine has already been successfully tested in Canada. Tidal current energy systems have been endorsed by leading environmental organizations, including Greenpeace, the Sierra Club of British Columbia and the David Suzuki Foundation as having ‘the lightest of environmental footprints,’ compared to other large-scale energy systems.

 

 

 

Vertical-axis tidal turbine – Canadian connection

A Canadian company – Blue Energy Canada Inc. – has completed six successful prototypes of its vertical-axis ‘Davis Hydro Turbine, named after its inventor, the late Barry Davis. Barry Davis got trained as an aerospace engineer, worked on the renowned Canadian Avro ‘Arrow’ project, as well on the equally-remarkable ‘Bras D’Or’ hydrofoil project of the Canadian Navy. Barry, then decided to apply his knowledge of hydrodynamics in creating a tidal energy generator. Barry received support from the Canadian National Research Council and successfully tested 5 turbine prototypes in the St. Lawrence Seaway and on the eastern seaboard. Blue Energy is presently raising funds for a commercial demonstration project of the Davis Hydro Turbine.

COMPARATIVE ENERGY DENSITY (kWh/m²)

SOLAR (PV)          1051 kWh/m²

WIND                   1000 kWh/m²

WAVE                   35-70,000 kWh/m²

BLUE ENERGY       192,720 kWh/m²

 

Horizontal-axis tidal turbine

Although, such tidal turbines were proposed during the oil crisis of the 1970s, the first tidal turbines began operating in the mid-1990s when a 15-kilowatt horizontal-axis tidal turbine was installed in Loch Linnhe on the west coast of Scotland, north of Glasgow. Now, two companies in the United Kingdom are planning to initiate horizontal-axis tidal turbine demonstration projects while another demonstration project has begun off the coast of Norway. A US company has also designed a working prototype. Horizontal-axis tidal turbines closely resemble wind turbines, except  that the turbine and blades are completely submerged in water.

 

Like the ocean dam models of France, Canada and Russia, vertical and horizontalaxis tidal current energy generators are fueled by the renewable and free forces of the tides, and produce no pollution or greenhouse gas emissions. As an improvement on ocean dam models, however, the new models offer many additional advantages:

 

- As the new tidal current models do not require the construction of a dam, they are considered much less costly.

- As the new tidal current models do not require the construction of a dam, they are considered much more environmental-friendly.

 

As the new tidal current models do not require the construction of a dam,further cost reductions are realized from not having to dredge a catchments area.

 

- tidal current generators are also considered more efficient because they can produce electricity while tides are ebbing (going out) and surging (coming in), whereas barrage-style structures only generate electricity while the tide is ebbing.

 

- Vertical-axis tidal generators may be stacked and joined together in series to span a passage of water such as a fiord and offer a transportation corridor (bridge), essentially providing two infrastructure services for the price of one.

 

- Vertical-axis tidal generators may be joined together in series to create a ‘tidalfence’ capable of generating electricity on a scale comparable to the largest existing fossil fuel-based, hydroelectric and nuclear energy generation facilities.

 

- Tidal current energy, though intermittent, is predictable with exceptional accuracy many years in advance.

 

In other words, power suppliers will easily be able to schedule the integration of tidal energy with backup sources well in advance of requirements. Thus, among the emerging renewable energy field, tidal energy represents a much more reliable energy source than wind, solar and wave, which are not predictable.

 

- present tidal current, or tidal stream technologies are capable of exploiting and generating renewable energy in many marine environments that exist worldwide. Canada and the US, by virtue of the very significant tidal current regimes on its Atlantic and Pacific coastlines

 

– proximal to existing, significant electro transportation infrastructure – is blessed with exceptional opportunities to generate large-scale, renewable energy for domestic use and export.

 

Tidal energy power systems are expected to be very competitive with other conventional energy sources, and excellent cost advantages arise from there being no pollution or environmental expenses to remediate nor are their fuel expenses (the kinetic energy of tidal currents is free). Further, ongoing maintenance costs are expected to be modest, as they are with other large-scale marine infrastructures, e.g. bridges, ships, etc., and a non-polluting tidal energy regime will qualify for valuable carbon offset credits. A 2006 feasibility report on tidal current energy in British Columbia by Triton Consultants for BC Hydro stated, “Future energy costs are expected to reduce considerably as both existing and new technologies are developed over the next few years.

 

Assuming that maximum currents larger than 3.5 m/s can be exploited and present design developments continue, it is estimated that future tidal current energy costs between 5C / kWh and 7C / kWh are achievable

Existing Hydrogen Transport and Storage Methods

Hydrogen is currently stored in tanks as a compressed gas or cryogenic liquid. The tanks can be transported by truck or the compressed gas can be sent across distances of less than 50 miles by pipeline

 

Safety is essential in the entire energy conversion process. This begins with production, storage, transport, distribution and utilization. Each energy form poses its own specific risk, which should be taken care. The safety of combustible energy carriers in their ignition, combustion, explosion and detonation behaviour when mixed with air is still under study.

 

Applications

Hydrogen is high in energy, yet an engine that burns pure hydrogen produces almost no pollution. NASA has used liquid hydrogen since the 1970s to propel the space shuttle and other rockets into orbit. Hydrogen fuel cells power the shuttle’s electrical systems, producing a clean byproduct—pure water, which the crew drinks. You can think of a fuel cell as a battery that is constantly replenished by adding fuel to it—it never loses its charge. A device has been designed to generate hydrogen to drive a cellular phone.

 

Fuel cells are a promising technology for use as a source of heat and electricity for buildings, and as an electrical power source for electric vehicles. Although these applications would ideally run off pure hydrogen, in the near future they are likely to be fueled with natural gas, methanol, or even gasoline. Reforming these fuels to create hydrogen will allow the use of much of our current energy infrastructure—gas stations, natural gas pipelines, etc.—while fuel cells are phased in.

 

In the future, hydrogen could also join electricity as an important energy carrier. An energy carrier stores, moves, and delivers energy in a usable form to consumers. Renewable energy sources, like the sun, can’t produce energy all the time. The sun doesn’t always shine. But hydrogen can store this energy until it is needed and can be transported to where it is needed.

 

Some experts think that hydrogen will form the basic energy infrastructure that will power future societies, replacing today’s natural gas, oil, coal, and electricity infrastructures. They see a new hydrogen economy to replace our current energy economies, although that vision probably won’t happen until far in the future.

Storage Of Hydrogen In Carbon Nanotube

Many new methods use carbon as a storage medium and bring us a step closer to the widespread use of hydrogen as a fuel source. Scientists are using various approaches to shape carbon into microscopic cylindrical structures known as nanotubes.

 

The first method of producing nanotubes uses an electric arc to vaporize a metal-impregnated carbon electrode.

 

The second method uses a laser to vaporize a heated carbon target that has been treated with a metal such as nickel, cobalt or iron.

 

The third method is known as catalytic chemical vapor deposition (CCVD), and researchers at Washington University in St. Louis believe this is the most promising approach. In the CCVD technique, a heated metal element breaks down a hydrocarbon gas (such as methane, ethylene, acetylene, etc.) into carbon and hydrogen. The hydrogen gas is released while the carbon is extruded as a nanofiber. The advantage of CCVD is that it is a low-temperature technique and is suitable for large-scale production.

Storage

One of the critical factors in nanotubes’ usefulness as a hydrogen storage medium is the ratio of stored hydrogen to carbon. According to the US Department of Energy, a carbon material needs to store 6.5% of its own weight in hydrogen to make fuel cells practical in cars. Such fuel cell cars could then travel 300 miles between refueling stops.

 

Researchers at MIT claim to have produced nanotube clusters with the ability to store 4.2% of their own weight in hydrogen. In recent months, scientists from the National University of Singapore have released figures for nanotubes and nanofibers that can store 10-20% of their weight in hydrogen. These results, when combined with new car manufacturing technologies have the potential of transforming our transportation industries.Single-walled carbon nanotubes are remarkable forms of elemental carbon. Their unique properties have stimulated the imaginations of many scientists and engineers to propose a wide range of applications.

 

Nanotubes do have a dramatic visual Impact. If beauty rests on symmetry, nanotubes have inherent beauty. Further, their cylindrical structures led to suggestions that they would be ideal gas storage materials. The appearance of these potential storage materials conveniently coincided with the revivification of interest in the hydrogen economy. The potential for coupling carbon-based storage materials to supply pure hydrogen to automotive fuel cell power plants was quickly seen.

 

Initial reports of experiments showing high levels of hydrogen storage were encouraging. Theoreticians were then quick to calculate the possible amounts of hydrogen that could be stored using arrays of tubes of various sizes and packing parameters. Since the appearance of the initial reports, the results have been varied and controversial. Some are higher, some lower; some imply physisorption, and some chemisorption. It is clear that storage is a complex issue, partly because the, materials are more far complex than the visual comprehension of the single ideal nanotube would allow.

 

Studies have been conducted and it has been found that purified Multi walled carbon nanotubes (MWNT) can be used for bulk storage of hydrogen. Multi walled carbon nanotubes have been synthesised by catalytic decomposition of hydrocarbon using a floating catalyst method. The mean diameter of the MWNTs was found to be 5.1 nm.

 

The MWNTs are then purified and hydrogen storage techniques are used. It is found that the gravimetric hydrogen storage capacity of purified MWNTs is much higher than that of as-prepared one which means that purification process is very important for hydrogen storage. This could be attributed to the fact that there is more exposure to more surfaces of the multiwalled nanotubes. The ends were seen to be opened up. This allowed hydrogen to more easily move into the hollow core of MWNTs. XPS spectra of C1s of the purified sample is narrower and has no notable peak in the range of high electron binding energy. This indicates that the sample is in simple chemical state. This simple chemical state of C and lower oxygen contained groups correspond higher hydrogen storage capacity of carbon nanotubes.

 

There are many questions that must still be answered regarding nanotube hydrogen storage: How do we make process more efficient at lower temperatures in order to increase supply and decrease cost? What is the capacity loss with each storage cycle? Can other forms of carbon produce the same results just as effectively? What additional applications can increase demand and research into nanotubes?

Storage of Hydrogen

Various technologies are available for the storage of hydrogen.

High pressure tanks : Hydrogen gas can be compressed and stored in storage tanks at high pressure. These tanks must be strong, durable Liquid Hydrogen: It can be stored as liquid but has to be kept at cold.

Hydrogen combines with some metals, which can result in higher storage capacity compared to high pressure gas or liquid.

Carbon Nanotubes can store hydrogen.

Challenges

For transportation, the overloading technical challenge for hydrogen storage is how to store the amount of hydrogen required for a conventional driving range, within the vehicular constraints of weight, volume efficiency, safety and cost. The performance lifetime durability of these systems must also be verified and validated. The main challenges are:

• Weight & Volume: – The weight and volume of hydrogen storage systems are 

   presently too high.

• Efficiency: – Energy efficiency is a challenge for all hydrogen storage approaches.

• Durability: – Materials and components are needed that allow hydrogen storage

   systems with a lifetime of 1500 cycles.

• Refueling Time: – There is a need to develop hydrogen storage systems with

   refueling times being very low.

• Codes and Standards: – Codes and Standards for hydrogen storage systems and

   interface technologies which will help commercialization and implementation on a

   large scale and assure safety, have not been established.

ENERGY OF FUTURE – HYDROGEN

As Hydrogen is to be produced from water, it is supposed to be one of the lightest, most efficient, cost effective and cleanest fuel on the planet, if the matured technology is developed. This is realistic since over 72% of the globe is covered with water and byproduct again is water. In other words Hydrogen economy starts and ends with water. It can avoid all harmful gases, acid rains, pollutants, ozone depleting chemicals and oil spillages due to conventional fuels. Use of Hydrogen can afford the development of clean and adequate energy for sustainable development of all.

 

Ever growing demand for energy and the rising concern caused by the use of conventional fossil fuels, call for new and clean fuels. Among all kinds of energy sources, hydrogen is the best choice as a clean fuel. The main advantage of hydrogen as energy source lies in the fact that its byproduct is water, and it can be easily regenerated.

 

Hydrogen is the simplest element; an atom of hydrogen consists of only one proton and one electron. It is also the most plentiful element in the universe. Despite its simplicity and abundance, hydrogen doesn’t occur naturally as a gas on the Earth—it is always combined with other elements. Water, for example, is a combination of hydrogen and oxygen (H²O). Hydrogen is also found in many organic compounds, notably the “hydrocarbons” that make up many of our fuels, such as gasoline, natural gas, methanol, and propane.

 

In its pure form, hydrogen is colorless and odourless gas. It is an energy carrier, not an energy source.

Production of Hydrogen

The various technologies that are involved in the production of hydrogen are

Thermo Chemical process.

Electrolytic process.

Photolytic process.

Thermo Chemical Process

1) Steam Methane Reforming: – High temperature steam is used to extract hydrogen from any methane source. This is the most common method of producing hydrogen.

2) Partial Oxidation: – Methods are being is explored in which simultaneously oxygen is separated from air and partially oxidizing methane to produce hydrogen.

3) Splitting water using heat from a solar concentrator.

4) Burning to generate gas, which is then reformed to produce hydrogen.

Electrolytic Process

Electricity is used to separate water (H2O) into hydrogen and oxygen.

Photolytic Process:

In this, Sunlight is used to split water. Two photolytic processes are being studied.

1) Photo biological methods: – This involves the exposure of microbes to Sunlight, split water to produce Hydrogen.

2) Photo Electrolysis: – Here, Semiconductors, when exposed to Sunlight & immersed in water, generates enough electricity to produce hydrogen by splitting water.

 

Thus Hydrogen can be produced in large scale and transported or locally produced depending on the method used. The delivery infrastructure for hydrogen will require high-pressure compressors for gaseous hydrogen and liquefaction for Cryogenic Hydrogen. These methods have significant capital and operating costs. They also have energy inefficiency associated with them.

 

 

Biorefinery

A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and chemicals from biomass. The biorefinery concept is analogous to today’s petroleum refineries, which produce multiple fuels and products from petroleum. Industrial biorefineries have been identified as the most promising route to the creation of a new domestic biobased industry.

 

By producing multiple products, a biorefinery can take advantage of the differences in biomass components and intermediates and maximize the value derived from the biomass feedstock. A biorefinery might, for example, produce one or several low-volume, but high-value, chemical products and a low-value, but high-volume liquid transportation fuel, while generating electricity and process heat for its own use and perhaps enough for sale of electricity. The high-value products enhance profitability, the high-volume fuel helps meet national energy needs, and the power production reduces costs and avoids greenhouse-gas emissions.

 

Conceptual Biorefinery

The biorefinery concept is built on two different “platforms” to promote different product slates.

The “sugar platform” is based on biochemical conversion processes and focuses on the fermentation of sugars extracted from biomass feedstocks.

The “syngas platform” is based on thermochemical conversion processes and focuses on the gasification of biomass feedstocks and by-products from conversion processes.

Water use for electricity generation

IEEE Spectrum: How Much Water Does It Take to Make Electricity?

Energy from Space-Based, Solar-Lasers

There are two new studies ongoing with the aim to investigate the feasibility of generating solar energy from solar panels borne by satellites. I can see the reasoning here: at the top of the atmosphere, the amount of the Sun’s radiation falling onto the Earth amounts to about 1,400 W/m^2 (Watts per square meter); however, the air-molecules absorb various wavelengths of light and so at any point at ground level, the intensity of radiation is attenuated. In northern Europe a reasonable estimate is around 150 W/m^2, somewhere quite sunny it is about 350 W/m^2 and in the Sahara Desert the energy is not far short of 1,000 W/m^2. Hence, out in space the full complement of the Sun’s power might be harvested.

In this particular concept being explored, a network of orbiting satellites would serve as energy transducers, capturing the abundance of energy from the Sun and sending it down to Earth in the form of a laser or microwave beam. (Mmmm… I wonder what the Health and Safety people would have to say about that?) . The original notion originated in the mind of Peter Glaser, a scientist working at Arthur D. Little in Cambridge, Massachusetts in the late 1960’s. No one is in any doubt that there are difficulties and drawbacks attending this particular type of technology, which smacks of “Star-wars”, and it is debatable just what the real economic benefit would be in practice.

The challenges of Space Solar Power (SSP) are various, but while concluding that the launching costs were too high, NASA (in 1995) decided to take a fresh look at the technology, possibly to attract financial and public support for its future activities. Since then interest in SP has accumulated, and a special study group at the National Research Council (NRC) has singled out several technological advances, which might be worth following-up on: (a) improvements in the efficiency of solar panels and the fabrication of light-weight panels, (b) progress in wireless transmission on Earth, notably in Japan and Canada, (c) robotics, deemed essential to run such an SSP assembly, has demonstrated significant improvements in terms of manipulators, machine vision systems, hand-eye coordination, task-planning and reasoning.

The panel concluded that significant breakthroughs are necessary before SSP technologies could produce energy in a cost-competitive way compared with Earth-based power generation. The final success of generating power on Earth from satellites depends “critically on ‘dramatic reductions’ in the cost of transportation from Earth to geosynchronous orbit (i.e. the altitude at which the orbiting period of the satellite is the same as that of a point on the Earth’s surface, meaning that from an Earth-bound perspective, the satellite stays in the same place at all times… you wouldn’t want it drifting off would you?!”). It further concluded the need for ground-based demonstrations of point-to-point wireless power transmission, and also the ‘desirability’ of ground-to-space and space-to-ground demonstrations… i.e. potential “Star-Wars” weapons.

We shall see, and I would rule nothing out as the world clutches ever more desperately at means to avoid drowning in the “Oil Dearth” era.

Related Reading.
“Bright Future for Solar Power Satellites,” by Leonard David. http://www.space.co./businesstechnology/technology/solar_power

German “Combined Power”.

A group of German scientists based at the University of Kassel has carried out a pilot-study which suggests that nuclear and fossil-fuel based energy can be phased-out and substituted by renewables, without interrupting the output from the national grid. As they point-out, renewable energy has certain limitations: e.g. cloudy or windless days are no good for solar or wind-energy. However, their innovative “combined power plant” draws its energy from 36 different kinds of plant, including solar, wind, biogas and hydroelectric designs, in an effort to prove that such a mix of renewable energy can yield a consistent and reliable output of power, under a range of prevailing weather conditions and according to non-constant demand for electricity as is the reality.

This has indeed been achieved on a relatively small scale so far, enough to power 12,000 homes, or enough for a small town/village. The village of Caversham, where I live, has a population of around 9,000 inhabitants (maybe 4,000 homes), if you include the effectively accommodative developments, i.e. with no shops or other amenities, and hence are pretty much dependent on car ownership. One significant aspect of the German design is that excess energy is used to pump water uphill into a large reservoir, which can be used during times of peak demand to drive hydroelectric turbines as an additional source of energy. The ability to thus store energy is a vital component of the overall scheme to provide a constant supply.

If this approach can be scaled-up, it is calculated that a total of 448 TWh/year might be produced in Germany, which breaks down to: 37.5% from 10,000 onshore wind turbines, 26.8% from 5,000 offshore wind turbines, 13.4% from photovoltaics (covering 20% of roof surfaces)and 22.3% from biogas, involving 17% of agricultural land. It is suggested that 40% of Germany’s electricity needs could be thus met by renewables by 2020 and 100% by 2050. I append a link to the full technical report below.

A very interesting approach. Of course there is around another 40% of total energy to be found for space-heating etc. and another 40% for transportation in the form of oil, assuming that the German break-down of energy use is similar to that in the UK. However, a relocalisation of German society, as will be the case across the entire world as oil supplies begin to fail our demand for them, substantially eliminates the latter component and Germany has substantial reserves of coal, which can underpin heating etc., even if its use can be avoided in electricity generation. The scheme will doubtless require a massive investment of money, energy and other resources to expand it to the future levels of electricity provision that are proposed, but such an integrated mix of supply sources may well be the best way forward, even at a local level.

Ultimately, in order to survive, all societies will have to be sustainable in terms of energy, food and all else they consume.