Post Carbon Toronto

Alternative Energy Sources

The decline of global oil production and North American natural gas production brings us face-to-face with two critical energy problems. One is to find an alternate source of energy for our transportation systems. The other is to find a substitute for our heating, electrical generation and industrial process heat needs.

Solar, Wind and Water Power

These are our only truely renewable resources and the resources on which we eventually must rely for almost all of our energy needs. Currently they provide a small but growing proportion of our energy supply. While there is limited potential for expansion of hydro power in most of the developed and developing world, we have not yet really begun to tap the power of solar thermal, photovotaic and wind power.

These sources can be used to produce mechanical, themal and electrical power, but except for hydro, these sources are diffuse and itermittent. Our ability to store electrical and thermal power is limited and can only be done at high costs. Only concentrated sources of electrical power such as hydro or perhaps biofuels are suitable for powering energy intensive industrial processes such as metal smelting and fabrication, glass and cement production. Unless breakthroughs in battery technology occur, none of these energy sources is suitable for powering cars, trucks and ariplanes.

Biofuels

We can create the liquid fuels we need for internal combustion engines from biological sources such as ethanol from grains or bio-diesel from oil seeds, but the amount of fuel that could feasibly be generated in North America is only about 10% of current consumption.

Current methods of generating ethanol from corn results in a marginal net gain in energy, that is, almost as much energy must be put in the process of growing and fermenting corn as we get out in the form of ethanol. Much more research into experimental process will be needed to make bio-fuels practical. Such fuels are likely to remain expensive.

The production of bio-fuels will potentially compete with food production unless we concentrate on plants that can grow in habitats that we don't currently use for food crops. Problems with maintaining soil fertility over time must also be addresses. Any bio-fuel supply will be subject variation in yields due to droughts, pests and other environmental factors.

Biofuels, in the form of fuel-wood plantations have been used in some places such as Brazil for fueling iron smelting. And biofuels in the form of pellets from plant sources such as switch grass have the potential to meet some of our residential heating needs.

 

Non-renewable alternatives

 

These energy sources may allow us to continue our way of life without change for a while longer, but not many decades longer. They are expensive technologies and the high capital costs for low production rates may make them inadequate as replacements for the decline of conventional fossil fuels, especially oil and gas. If we use coal to produce liquid an gaseous fuels, we will rapidly accelerate the depletion of this resource.

Liquid Fuels from Coal

Both non-renewable coal and natural gas can be used to create liquid fuels for our transportation systems, but such fuels will be very expensive and if used in this way our reserves will not last more than a few decades. Coal and natural gas are heavily used to generate electricity, space heating and smelting of metals, especially steel. In converting coal to liquid fuels, about 47% of the energy in the coal is lost in the conversion process.

The coal-to-liquids process is very capital intensive (thus expensive) and our capacity to ramp up production to meet transportation fuel needs is limited. We can probably not do so fast enough to meet the expected rate of decline in conventional oil supplies (Hirsch Report). If we use coal for producing liquid fuels, greenhouse gas emissions per kilometre will double.

Synthetic Gas from Coal

Synthetic gas can be generated from coal (and is used as the input to create liquid fuels from coal). Synthetic gas can also be used, and historically was used, as replacement for natural gas. However, our current gas distribution systems cannot be used to deliver synthetic gas because the high hydrogen content is incompatible with existing natural gas delivery pipelines.

Tar Sands

Tar sand deposits, principally found in Alberta, Venezuela contain very large amounts of hydrocarbon material in the form of heavy tars. These can be converted into conventional liquid fuels using an energy and capital intensive process of mining or steam extraction plus 'cracking' to upgrade the tar into a synthetic crude oil that can be further refined.

The net energy from these processes is relatively low, as little as 2 barrels for an equivalent of 1 barrel of energy input (often in the form of natural gas) and capital costs in Alberta are running as high as 100,000$ per barrel per day of production. Consequently, despite having commercially recoverable reserves nearly equal to those of Saudi Arabia, Alberta's production is only about 1/10 of that of Saudi Arabia. It will take about 15 years to triple that output and it is not expected that Alberta will ever match Saudi Arabia's peak production. Current tar sand production produces high levels of greenhouse gases.

Nuclear Power

At the current rate of world consumption there are only about 4 decades worth of proven uranium 235 reserves. It is likely that reserves can be expanded as uranium prices rise but may not be sufficient for a longer term, much expanded nuclear system. To support such a program it will be necessary to develop breeder reactor technology based on uranium 238, about 100 times more plentiful than uranium 235, or develop thorium cycle reactors.

In any case, nuclear reactors are expensive, capital intensive and take many years to construct. It will be difficult to build them at a rate that could supply sufficient energy to offset oil depletion.

Nor is nuclear energy, used primarily to generate heat and electricity, directly substitutable for liquid fossil fuels. To use nuclear energy to solve the liquid fuels problem we would have to either use the electricity they produce to create hydrogen through electrolysis of water and then replace our fleet of liquid fuel internal combustion engines with fuel-cell based vehicles, a hugely expensive proposition that would take many decades and for which we still do not have working technology, or use nuclear plants to displace all coal based generation of electricity and divert the coal to production of liquid fuels.

Nuclear Fusion

The development of nuclear fusion for the production of electrical power is still experimental and unproven after decades of research and billions of investment. The demonstration of a practical system is still decades aways and may never be achieved.

Hydrogen

Hydrogen has been promoted as the energy source of the future, powering the 'Hydrogen Economy'. That might be the case if large volumes of pure hydrogen were available on Earth, but that is not so. All but a very small amount of hydrogen is bound up in molecules, such as water (H2O). The chemical bonds have to be broken using a energy source before the hydrogen can be released so that it can be burned as a fuel. The amount of energy needed to break the bonds is greater than the energy that will be released when hydrogen is burned. Hydrogen is not an energy source. It is, at best, an energy carrier.

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