Innovation solves climate – growth can be sustainable.

Oil changed the course of history. For example, the British and American navies switched from coal to oil prior to World War I, allowing their ships to go further than coal-fired German ships before refueling. Oil also allowed greater speed at sea and could be moved to boilers by pipe instead of manpower, both clear advantages. During World War II, the United States produced nearly two-thirds of the world’s oil, and its steady supply was crucial to the Allied victory. The German army’s blitzkrieg strategy became impossible when fuel supplies could not keep up, and a lack of fuel took a toll on the Japanese navy.

Natural gas, a fossil fuel that occurs in gaseous form, can be found in underground deposits on its own, but is often present underground with oil. Gas produced with oil was often wasted in the early days of the oil industry, and an old industry saying was that looking for oil and finding gas instead was a quick way to get fired. In more recent times, natural gas has become valued for its clean, even combustion and its usefulness as a feedstock for industrial processes. Nonetheless, because it is in a gaseous form, it requires specific infrastructure to reach customers, and natural gas is still wasted in areas where that infrastructure doesn’t exist.

A final key development in world energy use was the emergence of electricity in the 20th century. Electricity is not an energy source like coal or oil, but a method for delivering and using energy. Electricity is very efficient, flexible, clean, and quiet at the point of use. Like oil, electricity’s first use was in lighting, but the development of the induction motor allowed electricity to be efficiently converted to mechanical energy, powering everything from industrial processes to household appliances and vehicles.

Over the 20th century, the energy system transformed from one in which fossil energy was used directly into one in which an important portion of fossil fuels are used to generate electricity. The proportion used in electricity generation varies by fuel. Because oil — an energy-dense liquid — is so fit-for-purpose in transport, little of it goes to electricity; in contrast, roughly 63% of coal produced worldwide is used to generate electricity. Methods of generating electricity that don’t rely on fossil fuels, like nuclear and hydroelectric generation, are also important parts of the system in many areas. However, fossil fuels are still the backbone of the electricity system, generating 64% of today’s global supply.

In sum, the story of energy transitions through history has not just been about moving away from current solar flows and toward fossil fuels. It has also been a constant move toward fuels that are more energy-dense and convenient to use than the fuels they replaced. Greater energy density means that a smaller weight or volume of fuel is needed to do the job. Liquid fuels made from oil combine energy density with the ability to flow or be moved by pumps, an advantage that opened up new technologies, especially in transportation. And electricity is a very flexible way of consuming energy, useful for many applications.

Back to the future – the return of the solar era

Fossil fuels allowed us to move away from relying on today’s solar flows, instead using concentrated solar energy stored over millions of years. Before we could make efficient use of solar flows, this seemed like a great idea.

However, the advantages of fossil fuels come with a devastating downside. We now understand that the release of carbon dioxide (CO2) from burning fossil fuels is warming our planet faster than anything we have seen in the geological record. One of the greatest challenges facing humanity today is slowing this warming before it changes our world beyond recognition.

Now that there are almost eight billion of us, we clearly see the impact of rising CO2 concentrations. Going back to the old days of relying mostly on biomass for our energy needs is clearly not a solution. Nonetheless, we need to find a way to get back to reliance on real-time solar flows (and perhaps nuclear energy) to meet our needs. There are so many more of us now, interacting via a vastly larger and more integrated global economy, and using much more energy. But we also have technologies today that are much more efficient than photosynthesis at transforming solar flows to useful energy.

The earth gets plenty of energy from the sun for all of us, even for our modern energy-intensive lives. The amount of solar energy that reaches habitable land is more than 1,000 times the amount of fossil fuel energy extracted globally per year. The problem is that this energy is diffuse. The sun that warms your face is definitely providing energy, but you need to concentrate that energy to heat your home or move a vehicle.

This is where modern technology comes in. Wind turbines and solar photovoltaic (PV) cells convert solar energy flows into electricity, in a process much more efficient than burning biomass, the pre-industrial way of capturing solar energy. Costs for wind and solar PV have been dropping rapidly and they are now mainstream, cost-effective technologies. Some existing forms of generating electricity, mainly nuclear and hydroelectricity, also don’t result in CO2 emissions. Combining new renewables with these existing sources represents an opportunity to decarbonize — or eliminate CO2 emissions from — the electricity sector. Electricity generation is an important source of emissions, responsible for 27% of U.S. greenhouse gas emissions in 2018.

However, unlike fossil fuels, wind and solar can only generate electricity when the wind is blowing or the sun is shining. This is an engineering challenge, since the power grid operates in real time: Power is generated and consumed simultaneously, with generation varying to keep the system in balance.

Engineering challenges beget engineering solutions, and a number of solutions can help. Power grids that cover a larger area are easier to balance, given that if it isn’t windy or sunny in one location, it may be somewhere else. Demand-response strategies can encourage customers with flexibility in their processes to use more power when renewable power is available and to cut back when it isn’t. Power storage technologies can save excess electricity to be used later. Hydroelectric dams can serve this function now, and declining costs will make batteries more economic for power storage on the grid. Storage solutions work well over a timeframe of hours — storing solar power to use in the evening, for example. But longer-term storage poses a greater challenge. Perhaps excess electricity can be used to create hydrogen or other fuels that can be stored and used at a later time. Finally, fossil fuel generation often fills in the gaps in renewable generation today, especially natural gas generation, which can be efficiently ramped up and down to meet demand.