Reduce, Replace, Renew. Part 2 A strategy maybe
Wed, 08/25/2010 - 18:16 — admin
Reduce, Replace, Renew. Sounds easy. Hard to do
The strategy to reduce, replace and renew sounds simple but is fraught with technological foibles and geo-political tangles. The big question is, can we wean ourselves from this awful habit of excess consumption? Can we actually lower our per capita energy consumption after having lived in the lap of luxury for so long?
The first treatment is substitution, like methadone is a substitute for heroin, biofuel is a substitute for petroleum. Why do we want a substitute? Because going cold turkey is tough and painful, besides we do love our internal combustion engines so dearly. We keep hoping that a solution can be found to allow us to have our precious cars forever. Biofuels reduce our dependency on petroleum and will at the very least move civilization toward being CO2 neutral but far from the final goal of removing CO2 from the atmosphere.
As with new drugs the first clinical trials will reveal a host of side-effects though thorough research and development will minimize any problems. Obviously when the USA mandated that Ethanol, a first generation biofuel be used extensively to stem America’s dependency on OPEC oil, it was not thought out thoroughly enough. First generation biofuels like alcohols are derived from a fermentation or refinement process of the carbohydrates stored in parts of the plant like the seeds, fruits or stems. In essence first generation biofuels compete for food crops hence the debacle we had with food prices.
In a finely tuned supply and demand system for food crops for human consumption, a country like the USA with 330 million people and as many large cars, allowing farmers to sell their crops for biofuel production instead is a godsend, for farmers that is. As a consequence the rest of the world suffers especially the poorest countries. It has been estimated that the amount of grain or corn needed for a thankful of a large SUV is enough to feed someone in Africa for a year. Has the the world gone mad? First generation biofuels is certainly not the way to go.
Second generation biofuels sometimes referred as biomass or cellulosic biofuels are a better answer as this technology uses the entire plant to produce biofuels. More importantly it need not be food crops, in fact the only requirement of this crop is that it be plentiful and grows faster than a spreading wildfire. Not only is it rapidly renewable, it also sequestrates the newly released CO2 that was building up in the atmosphere as plant material. Imagine that this clever system has exited for billions of years.
This particular technology has the ability to take away the oligopoly of OPEC and democratize this energy source to the poorer nations of the world though the powers that be might want see to it that it remains in the hands of only the rich nations.
A fuel for transportation
While biomass fuels have the ability to create fuels like synthetic diesel or ethanol or perhaps even petrol it is not the world’s most common form of energy because that has to be electricity. We talk about liquid fuel so much because we have a love affair with the internal combustion engine. When the internal combustion engine was invented there was no other powerplant that could be made so compact and transportable to be used in each and every automobile in the world.
It delivers decent energy conversion of about 17-25% meaning to say about 20% of all the energy stored in the tank of gas will be turned into useful propulsion but the rest is lost entirely is waste heat, ejected into the surrounding air. To keep things in perspective, a large scale oil or gas fired generator might achieve efficiencies about 30-35% but keep in mind that is all it does, produce electricity for a city efficiently.
Hybrid cars attempt to marry modern electronics with the traditional internal combustion engine to achieve efficiencies above 25% perhaps even 30% by a process of regenerative braking which captures the energy that might otherwise have been lost through braking. This captured energy is stored in a super capacitor to be used to accelerate the car again. This also allows the petrol engine to only operate in its most efficient load range, optimizing its use of petrol. It is a clever idea no doubt but is also complex and heavy, needing even more energy to make it in the first place at the factory level since it is essentially cramming two engines into one car.
An adaptation of the Hybrid is the Plug-in Hybrid. It began as a privately modified Prius Hybrid with Lithium battery packs that charges overnight on household current but is now officially planned as an official Toyota model. This is perhaps the most significant development in the future of the car as it neatly bridges the technological gulf between the traditional internal combustion engine and the electric vehicles of the future as it uses the excellent infrastructure of petroleum based fuels and the established widespread use of electric power in our cities. It marries the potentially zero emissions of electric vehicles and the dense, power packed energy from petrol for great distances and sustained power delivery.
So why the fascination with Fuel Cells and electric motors?
In the engineering world the keyword is efficiency and there is no better device than the fuel cell. Currently a fuel-cell stack for home use can achieve about 90% efficiency but this has to be clarified. A fuel-cell’s ability to convert Hydrogen to electricity is about 50%, better than out best conventional power generators. The rest is wasted as heat unless heat is useful to you. In an experimental program in Tokyo fuel-cells are used in homes to provide both heating and about 1-1.3kW of electricity. The heat from the chemical reaction that generates electricity is used to heat household water adding to the overall efficiency. But wait, where do they get their Hydrogen from? Read on.
In a car however the heat turns out to be much less useful unless it is in winter. The Fuel-cell stack might be able to produce electricity at 50% efficiency but that needs to be converted to mechanical energy to drive the car and this is achieved by an electric motor which can be 60-90% efficient. So overall the fuel-cell electric vehicle can be about 45% efficient (Tank to wheel) in theory about 10% more efficient than our current Hybrids. However if the vehicle is used in a test driving cycle like the NEDC (New European Driving Cycle) the true efficiency is more like 35% compared to 22% for a typical diesel under the same test. It is better but not the quantum leap many are hoping for.
Why Hydrogen cannot be the fuel of the future....
Moreover has anyone thought to ask where does the Hydrogen come from? It does exist naturally on Earth and is the most abundant element in the universe but is remarkably difficult to capture it from the atmosphere let alone attempt to store it. Sure pundits say there is an inexhaustible supply in our oceans existing as H2O. But scientists know better, as H2O is an extremely stable molecule. It would take tremendous energy to split H2 from O in a process called electrolysis. A lot of energy is lost this way just to get Hydrogen in its pure state and that is before it is stored as a gas or compressed, both which consumes even more energy. Slowly but surely this potentially perfect form of fuel is fast falling from favour as it delivers less energy than it consumes to produce and deliver it.
There is an easier way to get Hydrogen commercially by the process of Reforming. This process uses a hydrocarbon like natural gas or petrol and with a catalyst splits off H2 from its multiple C-H hydrocarbon chains to form H2 and CO and then converting CO to CO2. You do get Hydrogen rather efficiently but it has two big disadvantages, first that of additional CO2 production and secondly, a continued dependency on petroleum. Currently all fuel cells or fuel cell cars are fueled by this Reforming process being more a showcase for automakers’ Hydrogen powered cars than an actual proof of the Hydrogen-economy concept in its entirety as it still churns out CO2 and depends on petroleum. Moreover Platinum, the main ingredient of the catalysts in the fuel cells and reformers is also being rapidly depleted worldwide.
For those of you who are so taken by the promises of Hydrogen By the way Hydrogen is best used in Fuel-Cells and not firing up a modified V12 internal combustion engine delivering no improvement in conversion efficiency whatsoever squandering a difficult-to-get resource just to join the Hydrogen bandwagon.
There is no denying that theoretically at least Hydrogen is very possibly an excellent energy carrier but provided that we can make it, store it, liquefy it and deliver it at today’s fuel prices, without swallowing more energy in the process than it can deliver. So far that has been an insurmountable task and perhaps a futile one as there is something we are overlooking when being overawed by the Prima Donna called Hydrogen.
Why we may never get there…because of Electricity
The Hydrogen economy might be an elusive dream because there is already something we have in hand, something so common, so ubiquitous that it is often overlooked. If you haven’t realized what the common thread linking all these technologies is, it is electricity.
There are many reasons this might well be our magic bullet. Before we start talking about cars again, let us have a look at our current forms of energy sources.
On the non-renewable sources there is petroleum, natural gas, coal and thermo-nuclear power generation. What does it generate? Electricity. But these reserves of energy are depleting at an alarming rate and causing global warming at the same time. Thanks to the high price of fuel, it has sparked off a race for alternative renewable fuel sources.
Under the alternative, renewable or “green” energy banner is hydroelectric power, wind-power, tidal-power, geothermal and solar-heat or solar-electric power. Again all these forms generate electricity so begs the question why bother using it in any other form?
Read Part 3 Electric Dreams