Showing posts with label solar power. Show all posts
Showing posts with label solar power. Show all posts

Thursday, October 25, 2007

Combat Global Warming with Evaporative Cooling

Combat Global Warming with Evaporative Cooling - by Sam Carana

To combat global warming, wind turbines along the coastline could be used for the dual purposes of generating electricity at times when there is wind and evaporating water at times when there is no wind. Just a small breeze over the water can give the top water molecules enough kinetic energy to overcome their mutual attraction, resulting in evaporation of water and associated cooling of both water and air.

Such dual use of wind turbines can be implemented at many places where turbines overlook water; evaporation will work most effectively in hot and dry areas, such as where deserts or dry areas meet the sea or lakes. Evaporative cooling will add humidity to the air, which can also cause some extra rain and thus increase fertility of such dry areas as a beneficial side effect.

The energy needed to run the turbines can be obtained and stored in a number of clean, safe and renewable ways. ]

At times when there is plenty of wind, surplus energy from the turbines could be used to convert Water into hydrogen by means of electrolysis. Alternatively, bio-waste could be burned by means of pyrolysis to create both hydrogen and agrichar, which could be used to enrich soils. The hydrogen could be kept stored either in either compressed or liquid form, ready to power fuel cells that can drive the turbines at any time, day or night.

Another alternative is to run the turbines on electricity from concentrated solar thermal power plants in the desert. A desert area of 254 km² would theoretically suffice to meet the entire 2004 global demand for electricity. Ausra offers a solar thermal technology that uses the sun's heat to generate steam, which can then be stored for up to 20 hours, thus providing electricity on demand, day and night. Ausra points out that just 92 square miles of solar thermal power facilities could provide enough electricity to satisfy all current US demand.

Finally, there are some environmental concerns about wind turbines. There are concerns about carbon dioxide being released into the atmosphere in the process of making the concrete for the turbines. To overcome this, turbines could be made using alternative manufacturing processes, which can be carbon-negative. Furthermore, a recently completed Danish study using infrared monitoring found that seabirds steer clear of offshore wind turbines and are remarkably adept at avoiding the rotors.

In conclusion, wind turbines have a tremendous potential. They can potentially generate 72 TW, or over fifteen times the world's current energy use and 40 times the world's current electricity use. Offshore and near-shore turbines can make seawater evaporate and thus cool the planet, at times when they are not used to generate electricity.


References:


Ausra
http://ausra.com/

Wind power - Wikipedia 

Monday, October 15, 2007

Solar power and electric cars, a winning combination!

Who killed the electric car? It's an excellent documentary video, a must see! It was released on DVD to the home video market on November 14, 2006. 
http://earthissues.multiply.com/video/item/16 http://wikipedia.org/wiki/Who_Killed_the_Electric_Car%3F

There's more great footage at the Earth Issues website, such as a race between an electric car called the X1 against a Ferrari and a Porsche, and underwater recharging of an GM EV1 battery.

The electric car dates back to the 1830s, when Robert Anderson of Scotland invented the first crude electric carriage. Around 1900, electric cars outsold all other types of cars in America. Why? Because they did not have the vibration, smell and noise of gasoline cars and required neither gear changes to drive nor much manual effort to start (as with the hand crank on gasoline cars). The only good roads then were downtown and most car travel was local, perfect for slow electric vehicles with a limited range.

Now it's time to reinvent the electric car, for its convenience and for the positive contribution it can make in terms of the environment and global warming. Solar power and electric cars is a winning combination. Let me explain. Wind and solar power is not continuous, and this is where car batteries can help out, by storing electricity at times of high supply, to feed electricity back into the grid when supply is low. I can well imagine car batteries both drawing and feeding power to/from the grid at night. Intelligent net metering will assist with this.

How much solar power is needed for all this electricity? How much surface does it take to supply solar energy? The red squares on the image below show how much surface needs to be covered in theory by solar power facilities to generate enough electricity to meet the entire demand of respectively the World, Europe (EU-25) and Germany.

http://en.wikipedia.org/wiki/Image:Fullneed.jpg
Using concentrated thermal solar power, a mere area of 254km x 254km of desert land would theoretically suffice to meet the entire global demand for electricity for 2004.

The electricity can be transported nationwide over high voltage direct current (HVDC) lines, with line losses of about 3% per 1000 km (620 miles), adding $0.01 - $0.02/kwh to the local price of electricity.

Of course, it's hard for solar power to cater for peak demand during cold winter evenings, so it makes sense to complement solar energy with stored energy, wind energy, hydro energy, geothermal energy, etc, depending on local conditions. Anyway, as Ausra calculates, if solar facilities would store energy in molten salt, they could cater for almost all US day-and-night electricity needs, and would theoretically fit inside a square with 153 km sides. To additionally accommodate an entirely electrified vehicle fleet, the land area would grow to a square with sides of not more than 211 km.

From this perspective, the "how much surface" in the above question was better rephrased into "how little surface". Solar power alone could well provide enough energy for both our current electricity needs and can supply the additional energy needs to run our cars as well. Indeed, cars need not be bad from an environmental perspective. In fact, the combination of cars and solar power can be a winner for both. Again, let me explain.

Electricity can be stored in car batteries during the day, when cars are parked under roofs that are covered with solar panels that recharge the batteries. That could easily recharge the car battery enough for the owners to drive home and still leave sufficient power in the battery for other use. Note that 70% of Americans drive less than 33 miles per day. Late afternoon, when most people return home, they can plug their cars in at home for their own power use in the evening. Many will even have sufficient energy left to feed power back into the grid, selling electricity at top rates due to peak demand for power in the evening. Even if the battery became fully discharged in the evening, this still makes economic sense, as one can recharge later from the grid (during the night or early in the morning) when rates should be cheaper. Imagine there's a lot of wind during one part of the night. The meter will indicate that this is a good time for empty batteries to recharge. Conversely, when there is no wind in the evening, one will be able to get top dollars for feeding electricity back into the grid, pre-setting the battery to keep enough charge to get to work in the morning. As discussed, the car can then fully recharge from the solar panels on the roof of the parking place at work.

Sounds far-fetched? I'm very impressed with the Tesla Roadster, which has specs that many don't expect from electric cars, specifically an acceleration from 0 to 60 in about 4 seconds and a top speed of over 130 mph. It also looks great! You can recharge the battery at night in your garage and it will cost you as little a $2.50 in electricity for a full recharge.

With the Tesla, you'll be able to drive up to 250 miles on one single charge. This radius is achieved partly with regenerative braking that stores energy produced when braking. Recharging an empty battery with an EVSE system (operating at 70 amps) takes as little as 3.5 hours, but it also comes with a mobile-charging kit that lets you charge from any standard electrical outlet, e.g. in case you get stranded with an empty battery. Anyway, this short recharge time allows one to feed power back into the grid in the evening (when demand is high and supply from solar power sources is low) and still recharge later at night or early in the morning. Indeed, later at night rates are low, so it makes sense to recharge then. If sufficient wind is blowing, supply from wind turbines may be abundant in your area.

Electric cars requires less maintenance, since there are very few moving parts; you don't need to change engine oil, filters, gaskets, hoses, plugs, belts, there's no catalytic converter or exhaust pipe to replace. The Tesla uses Lithium-ion (Li-ion) batteries, for a number of reasons. They charge rapidly, have higher voltage, weigh less and last longer than Nickel Cadmium (Ni-Cd) batteries. Li-ion batteries do not contain polluting substances such as cadmium, lead or mercury. Li-ion batteries do not have the memory effect that makes that other batteries decrease in capacity when they are recharged before they are empty. Li-ion batteries do not have to be fully discharged, before they can be recharged, so one can top them up several times a day, e.g. at home or at the office. Nevertheless, Li-ion batteries will deteriorate over time, Tesla estimates that the battery pack needs to be replaced after about 100,000 miles. Also, cost is an issue; the Tesla Roadster 2008 model has a price-tag of $92,000 and the battery pack warranty is limited (I think it's only warranted for 100,000 miles, while it does cost thousands of dollars to replace). But battery cost is expected to come down in future, while at the same time battery capacity and performance is expected to increase over time.

Also have a look at Google's initiative on plug-in cars:

Google still uses plug-in hybrids, but it sets a trend away from using fossil fuel. There are also ethanol-electric hybrid cars; more than a year ago, Saab (General Motors Swedish car unit) already showcased such a car, combining an electric motor with an E85 Ethanol engine.

Google.org has issued a request for proposals to the tune of $10 million in order to advance sustainable transportation solutions.

Let me also pass on some links to the Rocky Mountain Institute in Colorado, at:

They envisage a "Hypercar," made of ultralight, super-strong, carbon composite material, which is 12x as strong as steel on impact. Manufacturing cars and trucks using these materials would dramatically increast the range of electrical cars.

Hydrogen is another way to store energy and is also promising in expanding the range of electric cars.

In conclusion: Just like we shouldn't rely on any single source of power (wind, hydro, solar power, geothermal, wave, tide and more), we shouldn't rely on a single way of storing power either. Apart from using car batteries for storage, we can think of capacitors, hydrogen, fly-wheels, compressed air, steam, sodium, molten salt, pumped-up water, etc. Clocks in the old days used weights to store energy. Similarly, bricks could be used as weights in larger contraptions. At even larger scale, we could use the Great Lakes as a reservoir not only of water, but also of energy. At times of peak supply of wind and solar power, surplus power could be used to pump water back from a lower to a higher lake, in order to use hydro-power at times when supply of other types of power is low. Free markets are good in sorting out which technology works best where and when. I have no doubts that the nuclear alternative will be prohibitively expensive once risk factors are better taken into account (accidents, waste management, terrorism, etc).

Tuesday, July 31, 2007

Solar and wind power in the sky

Solar panels and wind turbines only work when there is sufficient sunshine or wind. There are ways to overcome this disadvantage, such as storing the surplus electricity generated on sunny and windy days by pumping up water from a lower to a higher lake, to regain this energy as hydro-electricity later. 

Alternatively, car batteries could be charged when there is abundant electricity, to sell power back to the grid at better prices when there is high demand.

Another approach is to seek and harvest solar or wind power at locations where there is more permanent wind or sunshine. Wind turbines could be located in the sky. Bryan Roberts, professor of engineering at the University of Technology, Sydney, proposes clusters of wind turbines flying 15,000 feet high in the air. After studying the topic for 25 years, Roberts designed a helicopter-like rotorcraft to hoist a wind turbine high into the air, where winds are persistent and strong. Once there, the wind turbine is powered by its own electricity and keep itself in place, while transmitting electricity to the ground through a cable. Roberts has teamed up with San Diego-based Sky Windpower, which plans to produce a flying wind turbine with four rotors. The rotorcraft will go into the first layer of the atmosphere, called the troposphere. With GPS technology, the crafts can be kept in position to within a few feet.

Instead of using a cable to transport electricity down to the ground, electricity could also be tranferred through microwaves. Decades ago, Dr. Gerard K. O'Neill proposed to locate solar panels in space where solar power would be converted to low-density radio waves, sent to Earth and converted to electricity. O'Neill proposed this as part of a wider plan to colonize space. A publication by William Brown shows that the technology to transmit electricity by radio waves with a high degree of efficiency was already used as far back as in 1965.



Tuesday, May 15, 2007

Electricity for Europe

Here are three ideas to supply Europe with electricity:

1. Geothermal power from Iceland

In April 2007, the Icelandic National Energy Authority signed a deal with Energie Baden-Wuerttemberg from Germany, to work on electricity being transmitted to Germany from Iceland. A 1,200-mile ocean-floor cable is envisaged to carry electricity to Britain’s national grid before reaching Germany. The proposal is to drill 3.8km through the Earth's crust into the hot basalt below, in order to tap into temperatures of up to 600C and generate enough geothermal electricity to power up to 1.5 million homes in Europe.

See Iceland’s hot rocks may be power source for UK in The Sunday Times


2. Hydropower from Congo

The Grand Inga power station is a project to harness hydropower of the Congo River. Located near the mouth of the Congo River, with an output of 39,000 megawatts, Grand Inga would be the world's biggest hydroelectric scheme, generating twice the power of China's Three Gorges dam.

Three electricity superhighways would deliver power south to Angola, Botswana and South Africa, west towards Nigeria and north to Egypt and - ultimately - southern Europe. The project might cost $US80billion, but power delivered from Grand Inga to the Italian border would cost less than the current market price of electricity in Italy today.

See Africa waits on scheme to harness the power of the Congo River in The Sunday Times


3. Thermal solar power from Africa

The Trans-Mediterranean Renewable Energy Cooperation (TREC) was founded in September 2003. One proposal is for Thermal Solar Power to be generated in the deserts of Africa, for transmission by means of High-Voltage Direct Current cables to Europe, with losses of only about 3% per 1000 km, adding up to losses across the Mediterranean of 10-15% to Europe.













The above picture below is from:
http://en.wikipedia.org/wiki/Image:Fullneed.jpg

The red squares on the image represent the theoretical space needed for solar power plants to generate sufficient electric power in order to meet the electricity demand of respectively the World, Europe (EU-25) and Germany, based on data from a study by the German Center of Aerospace (DLR), P. 12 bzw. 26, 2005.