Can We Rely Entirely on Wind and Solar Energy?

Do you ever ask yourself when flipping the switch, where does that energy come from? Most likely it is from the reservoirs of fossil fuels created from the prehistoric vegetation buried for millions of years under the thick layer of soil. But as the demand grows every day, the challenge to provide enough energy is huge. Just by the end of the century, the global energy consumption is predicted to triple [1].

The deficiency of non-renewable energy sources is not the only problem, neither the most important issue we have to face. Burning of fossil fuels is, because it releases large amounts carbon dioxide into the atmosphere with the formidable consequence – global warming. The earth has already warmed up by nearly 1 degree Celsius. If the warming will continue to 2 degrees, we can expect major changes on Earth, such as sea-level rise in the tens of meters and an ice-free Arctic [2].

In order to prevent increase of global temperature by more than 2 degrees, the world’s energy emissions have to be limited nearly to 0 by 2050 [3]. That is why in the last few years humanity turn focus on clean and abundant sources of energy – the sun and wind.

The technological progress achieved when harvesting this energy during the last 5 years has been striking. And experts, such as Mark Jacobson and his colleagues from Stanford university, believe that our energy need can be covered solely from renewable energy [4].

“Abundant, clean and free.”

Solar and wind energy sound like the way to go for the bright future. But there is one aspect to consider, if we were to rely on them entirely. Can they provide enough base-load power?

Generating the base load power

The base load power plants constantly produce electricity. These highly efficient power plants run nonstop and are designed to cover around 30 to 40% of the electricity demand throughout a year. The remaining demand is supplied by peaking power plants, which run only when larger amounts of energy are needed – for example: during the day business hours.

The base load power is at the moment fueled by coal or nuclear. Renewable sources such as hydropower and geothermal power are also utilized by these power plants, but their disadvantage is that they are available only at some locations.

The solar and wind energy depends highly on the weather in the area, which makes them unreliable for the steady energy production required for the base load power plants.

Limitations to solar and wind energy

Solar and wind share two common characteristics that separate them from other energy sources. They are dilute and intermittent.

It is expected that the practical source of energy will be cheap and plentiful. Sun and wind are free but the process of capturing their energy is not. In fact, the diluteness means that they do not deliver concentrated energy. To produce one unit of concentrated energy from these sources therefore requires the use of specific materials to capture and convert their diluted energy.

Examples of specific materials used in the solar industry are silicon, boron and phosphorus. In the wind turbine construction is used rare earth metal called neodymium, steel and concrete. The acquirement of these materials comes with its own environmental impact and energy input.

The pressure on resource extraction to build solar and wind power plants further increases when comparing the capacity factors of coal power plant, which is 63.8%, with solar 15-19% or wind 20-40%. The higher the number is, the better the stability of performance is. In practice this means that to replace one coal power plant, we would need 2 to 3 wind turbines to deliver the same results [6].

The intermittent nature of wind and solar represents one of the main barriers to their exclusive use. The problem lies both in the storage and the immediate distribution.

Overcoming the challenge is possible (?)

Some scientists believe that the issue of intermittency can be easily solved by connecting diverse renewable sources of energy together in one grid, so called “smart grid”.

According to Mark Jacobson, a civil and environmental engineering professor at Stanford, and Mark Delucchi, a research scientist at the University of California, the combined energy supply from wind, solar and hydropower could be the key to supply enough power constantly. In this scenario, the hydropower would provide the energy backup in case solar and wind are too low [3].

Jacobson and Delucchi in their Plan to Power 100 Percent of the Planet with Renewables estimate,  that by merging the energy of 3.8 million large wind turbines, 90,000 utility-scale solar plants, 490,000 tidal turbines, 5,350 geothermal installations and 900 hydroelectric plants into one grid, we would not only get enough power to cover our global needs, but it would be even cheaper than the one obtained from fossil fuels.

When speaking about the electrical grid, it is important to refer to the research from the International Energy Agency (IEA) expressing a concern over the future adaptation of the electrical grid to higher loads of solar and wind energy.

Currently used grids can run without changing technical components with maximum 10% of renewably produced power. With higher proportion of renewable energy, the grid has to be optimized to be able to switch between different renewable systems. This might be a difficult and pricey quest for the developed countries with complex energy infrastructure already in place [5].

Large quantity storage

Where and how can we store the extra power generated during the time of abundance to be able to use it when the sun and wind cease to supply any for periods of time? The answer to this question has troubled many brilliant minds and still is… Currently used or tested methods are that first step to tackle this puzzle.

Concentrated solar thermal is one method of a solar energy storage. The system uses water or molten salt as a medium for energy storage. The basic principle behind it is the conversion of the energy from solar radiation to heat stored in the medium. Some of the newest solar thermal plants are able to store from 8 to 15 hours of energy [7].

Other possibility is the use of large batteries that get charged by the sun and provide energy when there is a lack of sunshine. Tesla is probably the best known in connection with some large-scale projects, such as the installation of a battery farm in Hawaii, which should be able to store 24 hours supply of energy [8].

Other big installation of 1.1 million batteries and 3.4 million solar panels is planned at the end of 2017 in the South Australia. The project should be the largest Australia’s solar farm [9].

Wind compressed air energy storage is one of the best large scale storage possibilities of wind energy. As the name suggests, the air is compressed and then stored in underground geologic structures such as salt caverns in deep formations for the periods of not enough wind. To generate electricity, the compressed air is heated and expanded, which drives a generator for power production [10].

Our civilization needs to embrace renewable energy on a scale and at a pace we’ve never seen before.

— Lester Brown, president of Earth Policy Institute

The development of new and more efficient solutions when it comes to solar and wind energy storage is an on-going process, as there is still a plenty of space for improvement. Even though, it is not an easy nor cheap task, some of the smartest brains from the field believe that our global energy demand can be powered entirely from these environmentally-friendly sources of energy.

As the 2011 Energy Report of the World Wildlife Federation (WWF) states, such a transition is technically possible within the next 40 years, while even saving $5.5 trillion per year through improved energy efficiency combined with renewable energy use.

Now it’s up to us to decide whether we will take the green path of innovation or stick our heads in sand and continue approaching with the increasing speed the finish line of the fossil fuel race.