We Albertans are widely-derided within our own country for being insensitive to the environmental consequences of our oilsands development. It is true that we have an out-sized carbon footprint and there are many Albertans that would like to see better environmental stewardship. In fact, despite the ugly pictures of tailings ponds around Fort MacMurray, a lot of Alberta looks like this:
We have invested a lot of money in carbon sequestration, the process of capturing carbon during the burning of fossil fuels and burying it, typically in old oil reservoirs. Of course, the environmental groups disapprove of this approach, preferring the oil to stay in the ground and the energy production replaced by renewables. Well, it turns out the environmentalists may have it all wrong, a future of wind and solar is just not possible. The villain is EROEI, energy-returned-on-energy-invested.
A recent paper by John Morgan, a prominent Australian expert on energy storage technology, lays out the problem. In order for a power plant to be viable, it must return more energy over its operational lifespan than it requires to build it. Dr. Morgan calculated the minimum EROEI of 7:1, once maintenance and operational requirements are included. Anything below that and the project makes no sense. Under current conditions, that is, an energy grid with ample baseload supply from fossil fuel and/or nuclear plants, wind and concentrated solar power (CSP) comfortably surpass that minimum EROEI. Interestingly, photovoltaic solar doesn't even achieve the threshold now, so you might want to reconsider any plans to install solar panels on your roof.
Anyway, a future without fossil fuels would require extensive energy storage capacity for times when the wind isn't blowing and the sun isn't shining, a problem fossil fuels don't have since the energy is already stored in the fuel. There are two main ways of storing energy, batteries and pumped hydroelectric. Batteries are more mobile but are ten times more energy intensive to produce per unit of energy storage. In other words, batteries will have to become an order of magnitude more energy efficient just to achieve the current EROEI of pumped hydroelectric and, of course, batteries require lots of rare metals which have their own scarcity issues to deal with when considering massive scale up. So, the best case scenario assumes pumped hydro, which involves pumping water to a place of higher elevation, then releasing it to run turbines like a normal hydroelectric dam. Even with the assumption of using pumped hydro for energy storage, wind power falls well below the threshold and CSP is just marginally above (and even then, only in ideal conditions for solar power). Nothing short of a miraculous new technology unlike anything we are currently working on can turn the trend line on this. We simply cannot maintain our civilization without fossil fuels or a huge increase in nuclear power generation.