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Solar energy is considered as the ultimate source of energy. In the last few years due to technology and abundant production of silicon, solar technology has become very commercially viable and it is rapidly approaching grid parity.

Effect of this could be seen in transportation also. Numerous solar vehicles have been tried or announced. Some of them are solar airplanes and solar powered ships. As a solar enthusiast, it looks very interesting to me. But, after looking at some of the traditional ‘flagship’ vessels and aircrafts, it is a different story. Some of the details are given below.

Largest aircraft ever built is the Soviet Antonov 225, with a maximum take off weight (MTOW) of 640 Metric Tonnes. But, practically the most widely used heavy aircraft is Boeing 747 with an MTOW of around 450 Metric Tonnes.

Consider the case of this aircraft becoming solar powered. The first choice is to fit solar panels on top of the wings and next, on top of the aircraft itself. How much area could be covered? As per Wikipedia, the wing area is around 550m2. The aircraft has a length of 70 metres and a width of 6 metres. So combining together, totally around 1000m2 would be available. With solar radiation of around 1000W/m2, total available solar energy reaches 1MW typically. For this exercise, we do not care about the cost of the solar cell, so let us consider one of the best triple junction cells at 40% efficiency. After installing, we could get 400KW of electricity.

Coming to the ocean front, the largest ship ever built was Seawise Giant or Knock Nevis with a DWT of 564763 Metric Tonnes. Her length was 458 metres and the deck area was 31541 m2. That one is an oil tanker, where as the largest container ship is Emma Maersk.

Let us repeat the previous exercise, Knock Nevis could collect a maximum of around 32MW of solar energy. With the best solar panels, around 12.8MW of electricity could be produced.

Note that this is the maximum solar power production. We are not at all considering about electricity storage system so that power is available when Sun is not shining.

Now let us see the energy requirement of these aircrafts and ships. Boeing 747 engines could produce around 1000kN of thrust where as it could carry more than 150 Metric Tonnes of fuel. During take off time, the fuel consumption rate is around 12000 US Gallons per hour, that is 10.25 kgs of fuel per second. With an energy density of 43MJ/kg, and a typical turbofan engine efficiency of 35 percent, that comes to 150MW of power production.

Coming back to Emma Maersk. The main engine produces 81MW and electrical generators produce 30MW. Fuel consumption could reach around 20 Metric Tonnes per hour. These ships carry around 5000 to 1000 Metric Tonnes of fuel.

That is the main point. Don’t think about a trip to Hawaii in a solar powered aircraft or cruise liner. A 747 requires around 400 times more power compared to what the best solar panels could produce, where as Emma Maersk requires around 8 times more. Even though solar could not be used for primary power, it could be used for a lot of auxiliary power applications.

Correction:The word ‘aircraft’ is both singular and plural. As per correct English, ‘aircrafts’ is not a correct word.

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Before we start, let us do a small exercise. Just go back one decade, to around 2002. That was the time when people started noticing more about Global Warming and Climate Change. If someone considers about getting rid of fossil fuels at that time he or she had a very limited options which were cost effective. Renewables like Solar were extremely expensive at around $6 per Watt, but Uranium was much cheaper instead. Public Confidence on Nuclear Energy was becoming better and better. Everyone agreed that Chernobyl was because of the faulty RBMK reactor design of the USSR. So Nuclear was a perfect option to avoid fossil fuels.

Now coming back to the current situation.

There have been a lot more concern about using fossil fuels nowadays because of Climate Change. But what are the cost effective alternatives? We do have the same options as before, mainly Nuclear, Solar and Wind power. But equations of Economics, Safety and Commercial availability are different. Let us take a look at how Nuclear take a stand in the game.

Types of fuels used in Reactors

Naturally available fissile material is only Uranium 235. Other two main fissile isotopes are Plutonium 239 and Uranium 233 but they have to be produced artificially. Plutonium 239 is produced from Uranium 238 and Uranium 233 is produced from Thorium 232 respectively and both of them require Neutron Capture and Beta Decay procedures. That means utilizing Breeder reactors and nuclear reprocessing. That is the reason why Uranium 235 is preferred as a nuclear fuel. But how much Uranium 235 is available? The answer is very less. 99.3% of the available Uranium is Uranium 238. In simple terms 140kg of natural Uranium is required to get 1kg of Uranium 235. Consider this large multiplication factor in determining the natural Uranium requirement.

Comparison with Renewables

Reserves: Uranium Reserves and Consumption Rate

Around 5000 kilotons of conventional reserves have been identified, at the same time, current World consumption is around 65 kilotons per year. That is enough for around 85 years at current consumption.
http://en.wikipedia.org/wiki/Peak_uranium

Main material used in Solar cells is Silicon and that is the second most abundant material on Earth.

Capital Cost of Nuclear Power

Nuclear Reactors are not cheap. They cost around $3 per Watt. For comparison Solar and Wind Power cost typically around $2 per Watt now. That is the current price, but one has to consider the fact that the price of Solar is going down at a very fast rate also.
http://en.wikipedia.org/wiki/Economics_of_new_nuclear_power_plants

Cost of Fuel: Depends upon Uranium Price

Price of Uranium went through a wave in 2007. During the beginning of 2000 it was around $20/kg and it climbed through $300/kg during 2007. It is some where around $110/kg for now. Major producers are Australia, Kazakhstan and Canada. This situation could potentially lead to yet another oil politics equivalent.

Renewable energy holds a great advantage because they do not require any fuel to operate.

Construction Time

Unlike many other power sources, Nuclear Power plants take a lot of time to get completed, typically in the order of 10 years or so. Where as, renewables could be installed in a very short time. This is yet another big drawback of Nuclear Power, a decision for a new nuclear power plant typically gets materialized in 10 years. Within that period much more renewables could be installed. As discussed above, one should consider the price drop rate of renewables during that time also.

Current share of Nuclear and Renewables

Nuclear power currently accounts for around 14% of world’s electricity (Wikipedia). Renewable Energy share varies from country to country. Germany is the world leader in Solar technologies while producing more than 20% power from renewables. In Italy it is more than 25%. For Spain, Wind Power is the single largest electricty source.

Requirement on Grid

Nuclear Plants are typically large capacity power sources located much away from load centres, increasing dependency on transmission systems, so as to upgrade or build new transmission grid. Renewables are very much decentralized and distributed. Also in many cases, they could be set up much closer to the actual load centres, reducing the requirement of Grid upgradation.

Security: The single most important point about Nuclear Energy

Nuclear took a real U-turn after the Fukushima incident. Germany decided to close all its reactors. Switzerland and Spain banned the construction of new ones. Unlike any other source of energy, this is a completely one sided problem of Nuclear power.

NIMBY Effect

Quite openly, most of the people including many of the “Go Nuclear” activists may not want a plant in their own neighborhood itself. This problem arises mainly because of the safety concerns and the land usage. Renewables are less affected by this, with the exception of some concerns about the aesthetic sense of wind turbines. Whatever it may be, it is much smaller in scale compared to Nuclear power.

Other Requirements

Nuclear is yet another form of thermal power plant. So it consumes a lot of water for its steam power cycle and plant ooling. Except for Solar Thermal system, renewables do not require water or any other resources.

A few thoughts

With all these details, I am not suggesting that we should stop Nuclear Energy and Research. But at the same time, considering Availability, Scalability, Safety and Cost, Renewables stand extremely competitive to Nuclear Energy.

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There have been a lot of focus about energy storage these days coupled along with solar and wind. As a coin has two sides, Energy Storage has both pros and cons.

Some of the main concerns I could gather are:

  • Prohibitively Expensive Capital Cost:
    Energy Storage systems are expensive to own. Cheapest solutions like Lead Acid Battery itself costs around $200 per KWh.
  • Usage of exotic Chemistries and Rare Materials:
    Many of the materials used are rare and expensive, for example Platinum is used as a catalyst in Fuel cells, usage of composite materials in flywheels, rare earths in superconductors etc.
  • Environmental issues:
    Batteries use environmentally unfriendly chemicals. Prime examples are the usage of Lead and Cadmium. Extremely reactive metals like Sodium and Lithium also are used.
  • Safety Issues:
    Many of the fuel cells and batteries should be operated at high temperatures. Reactive metals like Sodium and Lithium have safety concerns.
  • Limited Cycles:
    Most of the batteries could only be used for a limited number of cycles, for example Lead Acid Batteries have a limit of around 800 cycles.
  • Bad Depth of Discharge:
    They could not be 100% discharged, Deep Cycle Batteries could go to around 20% charge
  • Low Energy Density:
    Energy Densities are very low compared to both fossil fuels and biofuels.
  • Geographic location dependence: Especially for CAES and pumped hydro storage

Does that mean that we could dump the whole idea of energy storage itself? Hold on for a second, let us see what are the alternatives available.



What about maintaining the current status quo?
We are using fossil fules like petroleum, coal and natural gas to meet majority of our energy requirements. They have many advantages which could not be ignored for now, mainly comparatively cheap, excellent energy density, easy to store/carry wherever required etc. Most of the infrastructure required are already there.

To give an overview, currently huge amounts of fossil fuels are getting used. World usage of petroleum is around 86 Million Barrels per Day. To make it simple, 1000 barrels of oil is getting burnt every second !!!!! Coal usage is an astouding 6 Billion Metric Tonnes per year, that is 1 Metric Tonne per person. India alone uses around 3 Million Barrels of oil per day and 250 Million tonnes of coal every year.

So, if are ready to forget about pollution, climate change and expendable nature of fossil fuels, we still would be able to continue drinking petrol, eating coal and breathing natural gas. That is the only way to maintain current status quo.

Hydropower is really clean, should we use it?
Hydropwer is the single largest renewable energy source currently under use. It accounts for 20% of both India’s and World’s electricity production. Hydropower has a total potential to supply around 100% of installed capacity (around 3000GW) of the world. So water could barely lift the current load.
Hydro Potential of India
Hydro Potential of World

Nuclear Power Scenario
Nuclear Power provides around 14% of World’s electricity. Nuclear enjoyed lots of interests until recently. But after the Japanese Fukushima Nuclear Crisis, serious safety concerns have been raised.

How about using biomass like agricultural by-products, manure etc.
Biomass has got a huge potential and we should try to utilize them. A study says that India produces around 500 MMT of biomass per year and out of which around 150 MMT is surplus. This gives a potential of around 25000 MW electricity production for India.
Biomass Potential of India
But, looking carefully, biomass is really a low hanging fruit. It looks fantastic until biomass based systems try to go real mainstream. Once they reach the mainstream status, they could potentially create the following problems.

  • Limited amount of biomass availability because they are mainly agricultural by-products. So further scaling up from the above numbers would be really difficult.
  • Direct competition with food production for the availability of land if biomass production becomes a profitable business.
  • Stepping upon forest land for the same reason.
  • Difficult to use in transportation sector.

Can we complement the situation with Biofuels?
There are many different types of biofules available like bioethanol, biodiesel and biobutanol. Current main source of ethanol are sugar cane, and corn. Where as biodiesel could be produced from different oil sources like sunflower, coconut oil, palm oil etc. and also from Jatropha from marginal lands. But the best yield is given by different algae streams.
One study says that Jatropha based biodisel cound supply 22% of India’s petroleum demand.
Jatropha Potential of India

Considering the usage of land, it is essential to look at the overall efficiency from sunlight to biodiesel. It is practically less than 1%
Photosynthesis Efficiency

So, only algae based Biofules could reach sustainability. It is progressing but still it has not reached commercial status.
Other biofuel technologies like sugar cane ethanol, corn ethanol, palm oil and other biodiesel etc. have limited potential to fix the overall energy issues. Apart from that, they also contribute to the above mentioned problems: encroaching upon forest and farm land.

Our Earth is too hot inside. Geothermal energy.
Geothermal is another often discussed (pseudo) renewable energy and it could be considered as a baseload resource with no energy storage requirement. For commerical/quality power generation deep wells are required, on the other hand shallow wells could be used for heating purpose.
All these come with a few drawbacks. As per wikipedia, even though geothermal potential is much more than the current energy requirement, only a fraction of that is recoverable. Also quality varies through geographic locations. Apart from the economics, there are potential environmental drawbacks also. Chances of trapped carbon dioxide, sulphur dioxide etc. getting released to the environment is high. In addition to these gases toxic elements like Mercury, Arsenic etc. could get released. There have been concerns about increased earthquakes due to deep wells.
Environmental Effects of Geothermal Energy
Geothermal Resources

Wave Power, OTEC and Tidal Power
Wave Power, Tidal Power and Ocean Therman Energy Conversion (OTEC) have great energy potential. But they have not reached commercial status yet. Only pilot projects of a few MWs have been carried out so far.

How about Solar and Wind?
As per Harvard University, Wind Energy has a potential of more than 40 times the current World energy consumption. Where as Earth receives around 6000 times Solar Energy compared to the energy consumption. Wind Power has already reached grid parity in many cases and solar is gearing towards that. Lots of reserach and investments are taking place to make them go mainstream.
Global Potential for Windpower
Windpower Potential
Solar Potential

So, Sustainability and Climate Change have defined a clear goal…… Reduce the above oil and coal usage numbers as much and as fast as possible. A very challenging problem, much more than any “Rocket Science” ever achieved.

Considering both the current state of technology development and overall potential to meet the global energy demand completely, only Solar and Wind could be considered for the top positions. But their sustainability depends upon Energy Storage.

So as far as Energy Storage is concerned, apart from biting the bullet no other solution is existing in the long run. There is no other way, but to fix all of the shortcoming of Energy Storage.

Edited on 08/08/2011
I received a comment about Solar Thermal systems. Solar could include both Photovoltaic and concentrated solar thermal systems also.

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“Every block of stone has a statue inside it and it is the task of the sculptor to discover it” – Michelangelo

As of now, there are around 1.5 Billion people in the world without access to electricity grid, out ot which the share of India would come to around 400 Million people or around around 100 Million families. Majority of them live in the 80000 or so non grid connected villages in India.

They all depend mainly on Kerosene lanterns as the source of light. That makes Kerosene a very sensitive commodity in India. Kerosene is sold as a subsidized fuel in Government run ration shops for the poor people. Currently it is sold for around Rs. 12.50 per litre, but government gives around Rs.19.60 as subsidy on top of that to meet the actual open market price of around Rs. 32.00 Poor families are eligible to get around 6 lites per month at this subsidized rate.

Around 12 Billion litres of Kerosene are supplied to Ration shops annually and as much as 40% of that which is around 5 Billion litres are getting stolen to black market. The money lost by Indian government is around Rs. 10000 Crore (US$ 2.2 Billion) in subsidy itself. That gives around 7 Billion litres for the actual use.

There is another dimension for the “lost” kerosene. It is mainly used to adulterate petrol and diesel fuel. Adulterated petrol and diesel causes less mileage, higher maintenace cost, higher smoke and particulate pollution and emission.

Kerosene Usage Statistics

Summarizing Kerosene usage, Carbon Dioxide Emission and actual costs data.

Table1: Kerosene Statistics

Usage 7 Bn Litres Black 5 Bn Litres Total 12 Bn Litres
Energy Content KWh 70 Bn 50 Bn 120 Bn
CO2 Emission 17.5 MMT 12.5 MMT 36 MMT
Total Cost
(Rs 32.00/Litre)
INR 22400 Cr
USD 5000 Mn
INR 16000 Cr
USD 3560 Mn
INR 38400 Cr
USD 8540 Mn
Subsidized Cost
(Rs 12.50/Litre)
INR 8750 Cr
USD 1950 Mn
INR 6250 Cr
USD 1390 Mn
INR 15000 Cr
USD 3340 Mn
Govt. Subsidy
(Rs 19.60/Litre)
INR 13720 Cr
USD 3050 Mn
INR 9800 Cr
USD 2180 Mn
INR 23520 Cr
USD 5230 Mn

* Assuming: kerosne has an energy density of 10KWh/36MJ per Litre and it produces 2.5Kg of CO2 per Litre. USD 1.00 is around INR 45.00

* CO2 emission of India is around 1800 MMT, so this figure is around 2% of that.

Kerosene Lamp Efficiency

As per a study conducted by Lawrence Berkey National Labaratories, kerosene lamps energy consumption and light output vary a lot. In fact, a lot of kerosene is evaporated through the wick without getting burnt. Typical kerosene lanterns use around 5mL to 42mL of kerosene per hour, whereas light outputs vary from around 8 Lumens to 67 Lumens. This corresponds to light efficiency of 935 Lumen.Hour/Litre to 1914 Lumen.Hour/Litre. This leads to an energy efficiency of just 0.1 to 0.2 Lumen/Watts.

As a comparison, even an average incandescent lamp which many countries want to ban is more than 50 times better than these kerosene lamps. !!!!! To put it better, kerosene lamps are the costiest and dirtiest way to generate the same light output.

Apart from wastage of fuel, other problems like smoke, safety, burning hazard, pollution etc. associated with kerosene lamps are not discussed here. Also cost of kerosene lamps, running cost to buy wicks etc. are not mentioned.

Assuming average of around 1428 Lumen.Hour/Litre of Kerosene and 7 Billion Litres of usage, the total light produces is around 10000 Billion Lumen.Hours

Table 2: Electricity requirement from a baseload plant to generate the same light

Light Source Incandescent
10 lumens/Watt
Fluroscent
60 lumens/Watt
LED
100 lumens/Watt
Energy Usage
KWh/Year
1000 Mn 166 Mn 100 Mn
Energy Usage
KWh/Day
2750 x 1000 455 x 1000 275 x 1000
Constant Baseload
Equivalent
114 MW 18.9 MW 11.4 MW

This tables summarizes the power requirement of Incandescent, Fluorescent and Light Emitting Diode to produce the same amount of light. Light is normally required only in the evening time for around 5 hours. So 5 times peak power requirement could be assumed during evenings, where as no power is required for the rest of the time.

That means with a power plant of 1000 MW operating in the evening for 5 hours and using standard CFL lighting, 10 times more light could be delivered to the same people. (18.9 MW x 5 x 10 times light) This is not even 1% of the electricity production capacity of India. That is around 600 lumens of light per family compared to the meager 60 lumens which a kerosene lamp could provide.

Table 3: Power produced if the same kerosene is diverted to baseload power plants

7 Bn Litres
Usage
12 Bn Litres
Usage
Energy Content 70 Bn KWh 120 Bn KWh
Energy Content
in MW.Year
7985 MW.Year 13689 MW.Year
Standard DG Output
at 20% efficiency
1600 MW.Year 2700 MW.Year
Combined Cycle Gas Turbine Output
at 50% efficiency
4000 MW.Year 6800 MW.Year

This shows that the same kerosene could drive a 6800 MW Combined Cycle Gas Turbine based Power plant continuously for one year.

Using Clean Technologies for the same lighting scenario

As seen from above, to produce 10 times more light output using CFL, we require 4.55 Million KWh of electricity per day (189 MW baseload power plant equivalent).

Using Solar Photovoltaic
Being a tropcial country, India gets very good solar insolation of 5.5 KWh/m2/day or 2000KWh/m2/year average. Generating 4.55 Million KWh requires 830 MW Solar Panel. Currently solar modules are available below $2 per Watt. Maximum Power Point Trackers and inverters are available at around $0.60 per Watt and $0.75 per Watt respectively. Considering around $4 per Watt for all of these, it would lead to $3320 Million

Using Small Wind Power
With a capacity factor of 25%, the name plate capacity required to generate 189 MW of baseload power is 756 MW. Normally 2MW turbines are available at around $2 Million per MW. But small ones which generate a few KW are more expensive at around $4 per Watt. That comes to $3024 Million

Storage using Batteries
Standard Lead Acid Batteries cost around $200 per KWh. Assuming a depth of dischare of 50% it is required to have double the name plate capacity, so assuming $400 per KWh for the name plate capacity of 4.55 Million KWh, the requirement would be around $1820 Million.

Other Costs
There are many other expenditures associated like installations etc. In this case, many of them could be shared among different users. Assuming a cost of $40 associated with these, the total cost for 100 Million users would be $4000 Million.

Table 4: Summary of Clean Technology Costs

Energy Requirement
per Day
4.55 Mn KWh
Using Solar Systems 830 MW
at $4.00 per Watt
$3320 Mn
Using Windpower Systems 756 MW
at $4.00 per Watt
$3024 Mn
Storage Batteries 4.55 Mn KWh
at $200 per KWh
$1820 Mn
Other Miscellaneous 100 Million users
at $40 per user
$4000 Mn
Total Using Solar $9140 Mn
Total using Wind $8844 Mn

Conclusion:

To rephrase what Michelangelo said: “Money is there with the people, it is the task of the Government to reprioritize it”

References

http://www.interfaceflor.eu/internet/web.nsf/webpages/536_IN.html?OpenDocument&

http://articles.timesofindia.indiatimes.com/2011-01-30/special-report/28373372_1_kerosene-prices-ration-shops-kilolitre

http://articles.timesofindia.indiatimes.com/2011-01-27/india/28363076_1_kerosene-ration-shops-fuel-mafia

http://evanmills.lbl.gov/pubs/pdf/offgrid-lighting.pdf Table 1/Page 4

http://solarbuzz.com/facts-and-figures/retail-price-environment/module-prices

http://www.popularmechanics.com/home/improvement/energy-efficient/4321836


Edited on 26/07/2011:
I got a couple of comments about using biomass. Actually biomass gasifiers or digesters could be used to produce electricity also. One advantage of using this methods is that electricity could be generated as and when it is required. In many cases, this could be cost effective compared to solar or wind coupled with energy storage. Around 200 Million tonnes of biomass is used in India for cooking purpose itself.

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There have been a lot of proposals about having Solar Power Stations on Moon. The plan is to create a belt of solar modules around 11000km equator. The power will be taken to Earth using Microwave beams. After going through some of their ideas, I thought it was not an idea at all. Some of them were very basic so that I do not know how they over come them. Consider the following points.

  1. Earth receives 6000 times solar energy than we require, so there is no need to look outside.
  2. http://en.wikipedia.org/wiki/Space-based_solar_power#On_the_Moon These ideas are not new. They came back in around 1970.
  3. Current launch system costs are exorbitantly high, somewhere around $5000 per kg. Until systems like space elevators etc. become commercially available, it would be really expensive to launch these systems. Also note that, Moon does not have an atmosphere but it has a gravity of around 1.62 m/s2 which is 16% of Earth. So reverse thrust rockets would have to be used to land anything on Moon. Also these rockets and their fuel also have to be taken from Earth at the same cost of $5000 per kg.
  4. Actually only one side of Moon is visible, and Moon has a day of around 29 days. So for 14 days when the Sun is on the other side of the Moon, that means around what we call as New Moon times, no power or very little power could be sent to Earth.
  5. As per Wikipedia article, microwave beam power is around 23mW/cm2 which 25% of Solar radiation. So large area rectennas have to be used.
  6. Remember that Apollo program cost was $25.4 Billion actually (1973 report) but estimated cost in 2005 was around $170 Billion. (from Wikipedia)

Currently solar modules prices are going down very fast and very soon they would reach the landmark $1 per Watt level. There have been a lot of work going on in that area. Even Printed Solar Cells work is progressing . If these solar panel could be depoyed on everywhere on our own Earth, why do we need to taken them to Moon at all?

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