Solar and wind energy lie at the heart of all Net Zero programs. Other sources of energy can play important roles, but none of them are as crucial as solar and wind.
In spite of their importance, solar and wind have four major drawbacks.
They are intermittent;
They are not dispatchable;
They require a lot of space; and
They do not provide transportation fuels.
The first, and most serious, difficulty to do with solar and wind is that they are intermittent sources of energy. They are not “always on”. With regard to solar, it is night half the time and the sun often is not shining during the day. Wind power is equally intermittent. Sometimes there is no wind, and sometimes there is too much wind.
As a starting point we can assume that these energy sources are only available one third of the time. This is a huge problem, the impact of which can hardly be overs-stressed. Through use of “smart grid” software and long-range grid connections it may be possible to overcome this difficulty to some degree. But the reality is that, for every existing fossil fuel plant, at least two solar or wind facilities of the same capacity will have to be built in order to provide the needed power. Otherwise, energy storage facilities on a scale that is rarely contemplated will have to be built and commissioned.
Gail Tverberg says the following about the “going first subsidy”.
As more and more wind and solar are added to the grid, the impact gets worse and worse. Eventually, a larger and larger share of their output simply needs to go unused, because it is generated at times of day and times of year when it is not needed. Other providers need to fill in the electricity gaps at inadequate wholesale prices; this becomes an absurd demand. Whoever thinks this approach is “sustainable” is badly deluded in my opinion.
2. Not Dispatchable
The second difficulty to do with solar and wind is that the power that they generate is usually not provided when needed. This is not a problem for fossil fuel plants. As customers increase and decreased their demand for energy, so the plants can ramp up and down.
Once more, there is no easy solution to this dilemma. Currently solar and wind are such a small percentage of the overall energy picture that the existing fossil fuel facilities can, in effect, provide them with the "going first" subsidy just described. However, if solar and wind are ever to provide most of our power some means of meeting customer requirements as needed is required. Other energy sources, including nuclear and hydroelectric, can provide a good baseload of power, but they do not ramp up and down quickly.
We have just noted that the intermittent nature of wind and solar means that we will need massive energy storage capacity. Some of that storage will have to be quickly available. This distinction is important. Hydrogen, for example, can be used for storing energy. However, hydrogen cannot add power to the grid very quickly. To meet this need, batteries are required.
3. Land Area
A third difficulty with solar and wind is that they have a low energy density. This means that they take up a lot of land to provide the power needed. (This is why there is an incentive to install these facilities offshore where they do not interfere with agriculture and other important land uses.)
4. Transportation Fuel
The fourth concern to do with solar and wind is that they generate electricity. Yet many customers, particularly in the transportation sector, require a stand-alone fuel supply that can replace existing sources such as diesel, bunker fuel and aviation fuel. To satisfy this requirement, the solar/wind energy will have to be used to generate fuels such as hydrogen and ammonia. This is expensive.