Best energy sources

The most important consideration is whether the energy is readily available or needs to be released from a stored state.

The first problem with stored energy is that upon release, it adds energy to the environment, which, in the context of trying to reduce global temperatures, is counter-productive. Typical stored sources used to produce power are fossil fuels and nuclear. Heavy reliance upon these just adds substantial heat to the atmosphere.

Of course, these stored energy sources have another downside in that they are polluting, with fossil fuels contributing to carbon dioxide buildup, leading to further warming, and nuclear leaving highly dangerous radioactive products that we still don't know how to neutralise, thus dumping the problem on future generations.

Already released sources are sunlight, wind and water. The clear advantage of them is that the earth's ecosystems have already adapted to them, and importantly that adaptation has enabled us to exist and to thrive.

The closeness of the usage of the energy to its source is also important, as there can be adverse effects depending upon the source.

The main factor favouring local sources is the much lower infrastructure requirements and thus its cost savings for society. The general downside of having distance is that the energy released at the high-intensity generation locale is dumped into the atmosphere at the usage locale, which can create temperature-related effects upon the atmosphere there, such as temperature-inversion in Melbourne, Australia. Also, mass generation sites tend to be rather unsightly, and so typically need to be positioned well away from where people live.

Obviously, polluting or unsightly sources are best situated far from where they are used by people. Unfortunately, that requires transmission infrastructure to transfer the power, incurring increasing line energy losses and risk of line failure the further the distance. Conversely, local generation and usage can bring better coupling between them, minimised losses, and constraint of failure risks to its few users.

The other advantage of local generation is that the local ecosystem is less likely to be adversely affected. For example, sunlight normally falls on the ground, heating it up during the day, and releasing into the evening. With solar panels, the panels capture the energy instead, and coupled with storage, like batteries, is released for usage into the evening. Both scenarios have the same local absorption and release scenario, resulting in minimal effect upon the local environment beyond where the panels are erected and their output used.

To be really effective, energy generation needs to be coupled to some form of storage to handle interruptions or other downtime.

For electricity, batteries have rapidly become economically feasible. However, they require a lot of energy to manufacture, use a lot of toxic compounds, and have limited life. Using automated cranes and concrete blocks has proved successful with high efficiency, with the advantage of being able to be put anywhere, unlike hydro-power. For heat, heat-banks can store energy for later release.

The ideal is storage of high capacity, high energy density, high discharge rate, low loss over time, and low cost. No current technology meets all those criteria, so compromises are made to fulfil the situational priorities. Lithium-based batteries are good for transient and short-term storage, whereas hydro is good for short to long-term, but has limited location opportunities. Usually a combination of technologies is required for reliability.

Sources that have energy in latent form, such as fossil fuels, generally have higher energy density, but that is significantly offset by their far lower conversion efficiency to useful output. For vehicle use, their other advantage is that in use, their total loaded weight decreases, resulting in a progressive increase in overall usage efficiency as the fuel is used, just because less energy is required to move the vehicle at a given speed. That rate of efficiency increase will depend upon what percentage the loaded fuel is of the total vehicle weight.

Many focus on how much energy is produced to keep our societies afloat, but don't take into account how efficiently the energy is utilised.

The energy-efficiency Sankey charts for most countries show that only a third of the energy gets usefully used, with almost all of the waste from fossil fuels. The output of sources are what energy is potentially available at when used. For solar panels or wind turbines, that is the actual energy output. For fossil fuels, that is what is potentially available after burning. The big difference is that renewables output electricity, whereas for fossil fuels, there is a lot of lost heat during the burning process, leading to low conversion rates to usable energy.

The important consideration here is that uses relying purely upon electricity are generally the most efficient. For example, a car is only about 20% efficient when run on petrol, but 90% if electric. Fossil fuels are not efficient producers of electricity anywhere in the generation and usage chain. Their use has continued mainly because they have a high energy-to-weight ratio, which has facilitated their huge expansion in motor vehicle use where weight matters.

This means that when discussing replacing the energy produced from fossil fuels with renewables, far less energy needs to actually be replaced than if only considering the total potential output energy being produced. All this is about considering the total energy efficiency from source to when used. Aside from this wastage issue, fossil fuels are very polluting, such as petrol producing twice its weight in pollutants when used. These two issues work against relying upon fossil fuels.

There is energy required to make the solar panels or equipment to extract fossil fuels, and that is dependent upon the efficiency of the process and their replacement frequency. The lower this is as a percentage of the total lifetime energy output the better. Then there is the efficiency of the raw input to output process, where losses are usually as heat. Local solar panels are the best, as the input was heat that was going to the land where the panels were anyway, whereas too much heat as a byproduct of large-scale generation may be great enough to change local weather conditions.[1]

The risk to using any energy source has to be assessed.

The risk of having an adverse outcome is assessed both on the likelihood of it occurring and severity of its effects. Low scores for both is optimal. A frequent occurrence with low severity may be tolerable because it may be mitigated by other actions. Events of low occurrence but very high severity, such as nuclear power plant leakages, can preclude the reliable use of the technology altogether going forward. Existential threats, like climate change, must be avoided, even with a fuzzy severity. Having both means they should be avoided. Attempts should be made to mitigate both types of risk.

While the manufacturing of solar panels and wind turbines expends energy and may result in most of those currently existing going to landfill, their lifetime energy generation to usage ratio is higher than other sources, and their environmental damage and effect upon people is a lot less than the pollution from fossil fuels and the 5.3 million people killed a year by them, let alone their much greater generating and usage heat losses.

No matter what the source of energy is, the less required will mean less lost, and less pollution produced.

While fossil fuel companies are trying to make out that by making some minor tweaks to our individual energy use (carbon footprint), we can be effective in countering climate change, the reality is that the most effective changes will be made at government level, and that is by shifting emphasis and investment towards consuming less at a collective macro level.

We can make a very minor difference by turning off unused lights, but legislating to make businesses significantly favour enabling people to work from home will make major contributions to reducing total building erection and usage costs, simply because far less total lower-usage buildings will be required. Designing cities so that there is far less need for cars will drastically reduce the huge pollution from extra but underutilised buildings and overuse of roads. Then there is requiring manufactured goods to last longer, leading to far less replacement energy and resources used.

While making such choices at an individual level will make significant changes to our individual carbon footprints, collective action to force governments to ignore the wishes of most industries and force systemic lower-energy living, commercial and infrastructure scenarios will drastically reduce total and per capita national usage, and spur international efforts to make them more universal.

With these considerations, we are now in a position to rank sources as to their suitability to counter global warming.

Basically, local sources that are not in a latent form will have the least impact upon the earth's atmospheric temperatures, and requiring less energy overall will make the most difference.