Underground pumped hydro storage to increase renewables and the efficiency of thermal power plants

Illustration - Principle of the underground pumped hydro storage proposed by Pierre Couture. It can store power and regulate variations in renewable energy, among others, and is an essential component of intelligent electricity networks of tomorrow. (Illustration: Paul Berryman, from my book Driving Without Oil)

On 5 March 2009, Steven Chu, the United States Secretary of State for Energy, stated before a Senate committee his government's priorities in research and development. Five areas were identified and the storage of energy on a large scale is one of them. Storage units of appropriate size would compensate for daily variations of solar and wind, and increase the efficiency of thermal power plants. Energy storage is a key element to reduce greenhouse gas emissions as well of toxic emissions associated with electricity production.

Currently, the most used technology for large-scale storage of energy is pumped hydro. In its traditional version, there are two water tanks located one above the other, connected by an underground tunnel which houses a turbine that can operate in both directions. During periods of low electricity demand (eg at night) the electric motor-generator coupled to the turbine pump water from the lower reservoir to upper reservoir. In periods of high demand, we let the water flow from upper to the lower reservoir, which causes the turbine to generate electricity. In a well designed power plant, the movements of water between the two reservoirs cause a loss of about 20% of stored energy.

But to regulate the daily fluctuations of wind and solar power or to control the variations in demand throughout the day, we do not need to store more than 25% of the energy produced. Hence, regulation leads to a loss of only 5% of the total energy produced.


Illustration - Principle of a traditional pumped hydro storage facility. (source: Wikimedia Commons)

There are currently about 200 pumped storage facilities on the planet, totaling 90 GW of power, or about 3% of the installed capacity at the global level, according to the ESA (Electricity Storage Association).

The obligation to have a significant height difference between the two water tanks has brought many people to say that pumped hydro storage is a technology that could not operate on a large scale. As proof, the following statement

"Expanded use of this technology depends on the availability of suitable geography"

found in the "National Energy Policy Recommendations" of the IEEE-USA (Institute of Electrical and Electronics Engineers), dated 15 January 2009 (download HERE under the heading Energy and Environment).

But it seems that such an assertion is a lack of imagination, because one can very well build pumped hydro storage in the midst of vast plains or in the heart of a city. Just dig a deep well in the rock and build galleries at the bottom to get the second tank.

This is the concept which was proposed by Pierre Couture, a researcher for Hydro-Quebec and inventor of the modern wheel motor (previous post). Louis-Gilles Francoeur, journalist at Le Devoir has unveiled the project in an article dated 22 January 2004.

To avoid too large excavation for the galleries, it is expedient to settle at a greater depth. Pierre Couture recommended digging a well about 2 meters in diameter and three kilometers deep. Turbines that can be reversed and also act as pumps are placed at every kilometer going down, with a buffer cave behind each group of turbine-generators assembly (see illustration at the top of the post).

Calculations show that for a 1 GW of power lasting 10 hours, one must have 3 kilometers (1.9 miles) of galleries with a 20 meters x 20 meters (65 feet x 65 feet) opening, that is 1.2 million cubic meters, to store water at the bottom. The cost of such a plant would be in the range of $ 700 million to $1,000 million, and could regulate power plants with nameplate power of 3 to 4 GW.

If the facility lasts 50 years, we arrive ultimately at a cost below 0.2 cents / kWh of energy produced and regulated, which is only a few percent of the production cost.

Such pumped hydro storage facilities can be used in multiple ways. One can, of course, increase the percentage of renewable energies on a grid by regulating their inherent fluctuations. To reduce the need for too large storage facilities, we need to set up power lines to connect wind farms over thousands of kilometers, because there is always wind somewhere. The high voltage DC power lines are particularly interesting in this regard since they generate only 3% loss per 1000 km (600 miles). As for the solar power plants, they follow quite well the daily demand for electricity (more sun at noon). By placing them in desert areas, one ensures a minimum of cloud cover, which requires less storage of energy for the fluctuations. Most of the storage would be used to postpone to the night a part of the energy produced in the day.

Furthermore, pumped hydro is also interesting to increase the efficiency of thermal power plants. We know, for example, that gas-fired combined cycle plants can achieve an efficiency of 60%. Unfortunately we can not vary significantly the power of such plants to follow daily demand. We must use for that gas power plants whose efficiency is less than 40%. Thus we see all the benefits of coupling a pumped hydro storage to one or more gas-fired power plants. We could then use the most efficient combined cycle gas-fired power plants operating at constant optimal conditions. The daily fluctuations would be managed by the pumped hydro facility. In doing so, we would obtain 50% more electricity with the same natural gas!

With the additional electricity recovered one could close much dirtier coal power plants, waiting to close also, over time, the gas power plants and replace them with renewable energy.

Pumped hydro storage is an essential element of any smart energy policy! And with the underground concept proposed by Pierre Couture, it will become more and more interesting.

How much water to produce biofuels?

Illustration - Fresh water, a resource to preserve. (photo: Wikimedia Commons)

One of the main arguments put forward against biofuels is the high consumption of fresh water to produce them, at least with current technologies. But, as you will see, advanced plug-in hybrid of tomorrow will consume less than one liter of water per day.

To begin, let us look at a midsize car that normally consumes 8 liters of gasoline per 100 kilometers (60 miles) (fuel efficiency of 29 mpg). If we run it with 85% ethanol (E85), the largest commercial concentration, then we will need 11.2 liters of E85 (including 9.6 liters of ethanol) to travel 100 km. The highest amount is required due to the fact that ethanol contains only 2/3 of the chemical energy of gasoline, for a given volume.

Now, if to produce this E85 biofuel we use corn grains from Nebraska, we know that this corn requires 780 liters of irrigation water per liter of ethanol produced (see my book Driving Without Oil for more details). In addition, about 4 to 5 liters of water per liter of ethanol is needed for the manufacturing plant. In total, 785 liters of water are required for each liter of ethanol produced.

Thus, our traditional midsize car running on E85 ethanol in Nebraska consumes 7500 liters (1980 gallons) per 100 km (60 miles). This represents about 4,100 liters (1,082 US gallons) of water a day for someone who will travel 20,000 km (12,420 miles) per year. It is therefore understandable why many environmentalists are not warm to the idea!

But before you throw out the baby with the bathwater, let's see how we can achieve a consumption of less than one liter of water per day!

This requires, of course, the use of energy crops that do not involve watering, which is the case for wild prairie grasses, such as switchgrass. We have seen in a previous post that these perennial plants have roots 3 meters deep that are very effective in capturing soil moisture.

Furthermore, we have also seen in another post that advanced plug-in hybrid cars will consume 4 times less fuel than conventional cars when running on fuel, after their battery is discharged. But as these cars of tomorrow will run 80% of their mileage on electricity, they will actually consume 20 times less fuel.

But we have mentioned earlier that a traditionnal midsize car running with E85 ethanol mixt requires about 10 liters of ethanol per 100 km. The plug-in hybrid cars of tomorrow will therefore need only 0.5 litres/100 km on average (20 times less), which corresponds to 0.28 liters (0.6 pint) of ethanol per day for an annual mileage of 20,000 km (12,420 miles).

Finally, new ethanol plants will reduce their water consumption to about 3 liters of water per liter of ethanol produced, thanks to new technologies such as the one developed by the company Vaperma. This innovative company has developed molecular filters used to separate very efficiently water from ethanol without using distillation. They can save up to 45% of the energy normally used in an ethanol plant, while consuming less water. The decrease in CO2 emissions is also considerable.


Illustration – Vaperma molecular filter used to separate water from ethanol without distillation. The filters are made of polymeric membranes in the form of hollow fibers that are gathered to form the filter cartridge.

Furthermore, for thermochemical biofuel fabrication technologies (pyrolysis, gasification) manufacturing plants consume less than 2 liters of water per liter of biofuel produced.

There is also a new thermo-biological hybrid technology put forward by the company Coskata, which uses microorganisms to convert the syngas (mixture of CO, H2 and CO2) from a thermal process (gasification) into ethanol. According to Coskata, the process consumes less than one liter of water per liter of ethanol produced! This is less than for gasoline. To achieve such performance, Coskata does not use distillation but a molecular filtration process to separate water from ethanol, probably similar to Vaperma filters. In addition, the Coskata process does not include drying of tailings, as is found in the traditional corn ethanol plants, to make the solid protein supplement sold to the livestock industry. The distillation of the beer (fermentation mixture) and drying of tailings are the two processes that consume most water, by evaporation.


Illustration - Coskata thermobiologic process of making ethanol (Source: Coskata).

Ultimately, our advanced plug-in hybrid car traveling 20,000 km (12,420 miles) per year from which 16,000 km (10,000 miles) on electricity, will consume less than one liter (2 pints) of water per day, using biofuels based on tall wild grasses that do not require watering, and manufactured with the best technologies!

To put this water consumption of our future cars into perspective, it is interesting to know the consumption of water per kilogram for different food products. The table below summarizes the results found in the book by David Pimentel and MH Pimentel, Food Energy and Society, CRC Press, 2008. It shows that we need 43,000 liters (11,360 gallons) of water to produce 1 kg (2,2 lbs) of beef, which means more than 6,000 liters (6,000 quarts) of water for a steak of 150 grams (5,3 ounces)! So it is not the 1 liter (1 quart) of water per day consumed by our car that will endanger our freshwater resources. Too large portion of meat in our diet, particularly red meat, is much more worrying in this respect ...

Illustration - Number of liters (1 US gallon = 3.785 liters) of water required to produce one kilogram (2.2 lbs) of different foods, according to the work of David Pimentel, professor of ecology and agriculture at Cornell University.

Is There Enough Lithium for the Batteries of 1 Billion Plug-in Hybrid Electric Vehicles?

Illustration – Salt « mining » in the Salar of Uyuni in Bolivia, the largest lithium reserves in the world (source: Wikimedia Commons)

The introduction of Li-ion high-performance batteries was, without doubt, the trigger for the imminent revolution in road transport. But is there enough lithium to power a billion cars on the planet, ultimately?
To respond, we must know first that according to the U.S. Geological Survey (USGS), the reserve base for lithium on the planet is estimated at 11 million metric tons. But these estimates do not include reserves of Argentina reported recently by the company Orocobre (3 million tons). A very informative report on the global lithium reserves and markets is available from this company. This report by Martin Place Securities can be downloaded by clicking on the news dated March 31, 2008 about Project Olaroz. In United States, the company Western Lithium is currently conducting geological expertise of a large clay deposit of lithium in Nevada, at King Valley. The estimated reserves are 2.08 million tonnes of lithium (11 million tons of lithium carbonate, Li2CO3) and they are not included neither in the USGS evaluation. Updating the USGS assessment, there is therefore a global reserve base of 16 million metric tons of lithium.

In addition, the USGS reports a global annual production of 25,000 metric tons of lithium in 2007. At this rate of exploitation, there would be enough lithium for several hundred years. This abundance and the low price of lithium (8$/kg) obviously did not stimulate the exploration of new deposits. We can therefore expect that global reserves are more than 16 million tons.

Now, in the Martin Place Securities report mentioned above, we learn that the percentage of lithium recovery from the reserves is about 50% on average. Thus, counting 16 million tons of reserve base it means that 8 million metric tons of lithium are available for the industry.

75% of the Lithium reserves are in the form of salt, mainly lithium carbonate from the deserts of salt. The key deserts are found in South America (top of photo) and also in Tibet. Lithium carbonate is the raw material used by the battery industry (5.3 kg carbonate give 1 kg of lithium).

Now, for a midsize plug-in hybrid car a battery giving it a range of 100 km in electric mode currently requires storing 20 kWh of electric energy. In addition, the company LG Chem, which provides the Li-ion batteries for the GM Chevy Volt, through its subsidiary Compact Power, says on its website (in the Technology section at the FAQ page http://www.compactpower.com/faq.shtml) that they need 140 g of lithium per kWh of battery, giving 2.8 kg of lithium for 20 kWh, which we round up to 3 kg (6.6 lbs). Let us recall that with this 3 kg (6.6 lbs) of lithium, a midsize car can run 100 km (60 miles) in electric mode with today commercial technologies.

Now, hybrid cars of the 2020s will be lighter, more aerodynamic and will be equipped with wheel motor powertrains that consume considerably less energy. These midsize cars of tomorrow will consume about 12 kWh/100 km instead of 20 kWh/100 km as mentioned above (see my book Driving without oil). So one will need only 2 kg (4,4 lbs) of lithium per car [for 100 km (60 miles) all electric range] in 2025. Thus, for a billion vehicles (there are currently 800 million on the planet), we would need about 2 million tonnes of lithium, a quarter of global reserves base available after extraction.

There is therefore enough lithium on the planet for plug-in hybrid cars. But if we wanted to use all electric cars with batteries providing a 400 km range (240 miles), then we would have problems. It is always preferable to use the smallest battery possible to travel 80% of our mileage.

Now, we must realize that the Li-ion batteries can be recycled at 95%. Finite lithium reserves can not therefore be compared with finite oil reserves, since oil is totally lost in an internal combustion engine.

Some critics of electric mobility also point out that about 60% of lithium world reserves are located in South America and that it is a similar situation than the Middle East for oil. But, as lithium price goes up steadily, more and more companies will search for new deposits. Only in the King Valley deposit in Nevada, there is sufficient lithium for 500 million advanced midsize cars with an all electric range of 100 km (60 miles).



Illustration - A mining project of the company Lithium Canada Corporation, near Val d'Or in Quebec, could produce enough lithium to equip all Canadian vehicles with a battery giving a range of 100km (60 miles) in electric mode. (source: Lithium Canada Corporation)

The company Lithium Canada Corp. also uses an old mine near Val d'Or Quebec. It expects to produce the equivalent of 55 million kg (120 million lbs) of lithium, enough for 25 million advanced midsize cars with a range of 100 km (60 miles) in electric mode, which would fulfill the needs of all Canadians.

Where to find land for biofuels?

Illustration - The livestock industry emits more greenhouse gases than all vehicles on the planet. (photo: Wikimedia Commons)

When we talk about biofuels, people are afraid of losing land to feed people and say that it makes no sense. But let us try to be objective and to look at our land management on the planet from a broader perspective and see if we could not do better.

First, according to a report of the United Nations published in 2006, 70% of farmland in the world are dedicated to the livestock industry [H. Steinfeld et al., Livestock's long shadow, Food and Agriculture Organization (FAO), Rome 2006]! These lands are divided into pastures and cultivated areas to feed livestock (33% of cultivated land on the planet).

Moreover, according to the same report, the livestock industry is responsible for 15% to 18% of anthropogenic emissions of greenhouse gases (GHG) expressed in CO2 equivalents. But what we need to know is that all road vehicles in the world are responsible of approximately 12% to 13% of greenhouse gas emissions (including GHGs to produce fuel). So, the livestock industry emits 50% more GHG than road vehicles!

Another factor to consider also is that one hectare of land (1 hectare = 2.47 acres) produces about 25 kg (55 pounds) of beef protein, whereas the same hectare can produce 400 kg (880 pounds) of vegetable protein with soy, 300 kg (660 pounds) of protein with rice and 150 kg (330 pounds) with wheat. Not to mention that to produce 1 kg (2.2 lbs) of beef, it takes more than 40,000 liters (10,566 US gallons) of water, which means more than 6000 liters (1,585 US gallons) of water for a steak of 150 grams (5.3 ounces) (see the website of the organization Compassion In World Farming www.ciwf.org.UK, in particular The report Global Benefits of Eating Less Meat, 2004)! Too much meat in our diet is therefore a blatant waste of our planet's resources in agricultural land and fresh water, not to mention other resources such as fossil fuels (natural gas for fertilizers and oil for machinery).

We must know these facts if we are to make informed decisions about the use of our farmland.

In my last book Driving without oil, I recommend to reduce our meat consumption by 15% (one day a week without meat). In doing so, it releases more agricultural land than necessary to produce biofuels equivalent to 5% of petroleum fuels currently used. Now, 5% that's all we need from energy crops to remove oil from the road transport (see previous post).

In closing, we must not forget that by reducing our consumption of meat to produce second generation biofuels, we DOUBLY reduce greenhouse gas emissions, since the livestock industry emits more than all vehicles on the road.

Carbon negative Biofuels: 2 - Polyculture of wild grasses

Illustration - The wild prairie grasses have abundant and deep roots reaching 3 to 4 meters under the surface. (source: United States Department of Agriculture, the depth in meters was added by the author of this blog)

With petroleum fuels, one takes carbon that was underground, burns it and constantly increases the CO2 content of the atmosphere. The idea behind biofuels is not to emit CO2 from carbon sequestered in geological formations (géocarbone) and use in place of biocarbon found in plants. Biocarbon enters in what is called the carbon cycle, where the carbon we send into the atmosphere by burning biofuels is reabsorbed by plants that grow to produce biofuels. It does not constantly adds to the atmosphere if we do not use fossil fuels to produce biofuels. In this ideal case we say that biofuels are carbon neutral.

This ideal case is not achieved in practice and net CO2 emissions are also associated with biofuels, but at lower levels than CO2 emissions from petroleum fuels. This reduction is only 20% for ethanol produced from corn, and some even say it is zero if one takes into account the greenhouse gas involved in the fabrication of the machinery. Add to this the problems of land degradation and water pollution caused by fertilizers and pesticides, and we understand why many environmentalists do not like biofuels.

However, second-generation biofuels have the potential to reduce greenhouse gas emissions by 80% to 90%, using the whole plants instead of only grains and fruit, as it is currently the case. But the problems of degradation and soil erosion by intensive monocultures must also be taken into account.

To solve these issues, in the last few decades researchers have studied the advantage of wild tall prairie grasses, as switchgrass. First, these plants are perennials, they do not need to be sowed each year, such as corn or soybeans. In addition, these grasses have well-developed and deep root systems (illustration at top of post). With these two features, the wild prairie grasses protect soil from erosion, rather than increasing it as do the intensive in row monoculture of annuals.

Furthermore, wild grasses need not be watered because their roots are very efficient to retrieve soil moisture, 3 to 4 meters deep. By comparison, corn requires often watering with several hundreds of liters of water per liter of ethanol produced.

But the cultivation of wild grasses becomes particularly interesting when it is grown in a mixture, including plants that fix nitrogen. This was studied by researchers at the University of Minnesota for 10 years on degraded land. They cultivated 152 different parcels of land containing different mixtures of up to 16 different plants in the same plot. The astonishing results of their study were published in 2006 (Tilman, Hill and Lehman, Science, Vol. 314, December 8, 2006, pages 1598 to 1600).

First, the quantities of fertilizers and pesticides required are significantly reduced compared to corn and soybeans, as shown in the chart below, taken from their publication. The word "Biomass" in this graph represents the high diversity mixture of 16 different plants.



Now the surprise is that second generation biofuels from such high diversity prairie grasses mixture are strongly carbon negative! This means that in addition to avoid net emissions of CO2 in the atmosphere (carbon neutral), these cultivations are literally removing CO2 from the atmosphere to reduce its concentration. The reason is simple, the carbon is stored underground in large quantities in the roots. It's a bit like charcoal in the Terra preta, buried by the Amazon natives (see previous post).

However, to get stong carbon negative biofuels (-150% to -250%), we must cultivate several plants together. For example, plots with a mixture of 16 plants store 31 times more carbon in the soil than in monoculture plots!

No, definitely, biofuels of tomorrow will have nothing to do with those of today, hence the importance of not throwing the baby out with the bathwater. Sustainable development of biofuels is entirely feasible, if done intelligently and if we produce only small quantities.

In my last book ”Driving without oil”, I demonstrate that cultivating energy crops to produce biofuels equivalent to 5% of current petroleum fuels would be sufficient to stop oil consumption in road transport. The electricity networks would, of course, provide the main ”fuel”. One would also use municipal waste, forest residues and recycled oils and fats from the food industry to produce biofuels, which can easily supply the equivalent of 2.5% of current petroleum fuels, for a total of 7.5% in biofuels (including dedicated energy crops).

Carbon negative biofuels: 1-The lesson of ancient Amazon natives

Illustration - Micrograph of a piece of charcoal (biochar) showing its extreme porosity, small holes are about 1 / 100 of a millimeter in diameter. It is an ideal environment to retain water, nutrients and microorganisms, increasing soil fertility. (Source: Best Energies)

Over the past ten years, agronomists and environmentalists are increasingly interested in Amazon Terra preta, an extremely fertile black soil resulting from amazing agricultural practices of ancient natives.

Their secret was charcoal buried deep in the soil, hence the name Terra preta, in Portuguese. The appearance of porous charcoal, also called biochar, helps retain nutrients, water and microorganisms. These features facilitate the growth of plants and reduce the need for fertilizer while reducing more than 50% the emission of nitrous oxide, a gas 300 times more potent for global warming than CO2.

To produce biochar, one uses a process of thermal decomposition of biomass called pyrolysis, which involves heating wood or crop residues in an enclosure with scarce oxygen environment. Combustible gases are then released containing, among other things, hydrogen and methane, which are partly used to produce the heat required by the process. A bio-oil is also formed after processing and cooling, that can used in heating furnaces. You can also turn this bio-oil into biofuels more suitable for transport, such as diesel and synthetic gasoline or ethanol with proper thermo-catalytic processes. One obtains then second-generation biofuels.



Now, when we bury biochar, in addition to fertilize the land we also sequester in the ground some CO2 from the atmosphere which had been absorbed by plants. It helps to remove greenhouse gases, a bonus specifically sought these days! The combination of buried biochar and biofuel production, therefore makes these biofuels carbon negative, which is still better than carbon neutral biofuels. Professor Lehmann of Cornell University estimates that implementing these practices on a large scale, could both produce biofuels and withdraw annually 9.5 billion tonnes of carbon from the atmosphere by 2100. That is more than what we send in the atmosphere today in the world by burning fossil fuels!

For more information, please visit Terra preta site and the site of The International Biochar Initiative (IBI), where we find the illustration of the pyrolysis process shown above. In addition, the following video is an excellent documentary on the subject.

Terre preta - biochar