Mechanical work is good for systems where large power but imprecise operation is needed. There is not much precision in rotation of a fan or working of a pump but they consume a lot of energy.
Electrical work on the other hand is invaluable where precision is needed on an electronic scale. LED, electronic circuits ,TVs, computers can't directly work on heat you need electrical energy for them.
Similarly all modern communication systems are useless without electricity. it is for these systems we need to ensure a continuous sustainable electrical supply.But here too heat has a role to play
if you think about it most of the energy generated today is by steam turbines at around 40 to 60% efficiency. we can generate electrical energy from stored thermal energy that matches the efficiency of turbines and transport them through the grid via existing infrastructure. The only difference being the heat source that was chemical ,nuclear is now stored heat.
The systems( battery ,engine, heat exchangers) that we develop for use in mechanical work can be used in generation of electrical energy just that they need to be coupled to an AC or DC generator. There are trade offs to be made in the choice of generator as well but the important thing is that we can achieve stable efficiency that matches the efficiencies of nuclear /steam power plants .This is better than what solar cells can do at the moment.
Does it make sense to store electrical energy as heat?
In some very specific cases it does.
wind always produces mechanical work that can be transformed to electrical energy. Either this energy can be transmitted for immediate use or stored in a battery.
As good as lithium-ion batteries are ,they are still expensive in terms of money and materials used plus their lifetimes are short as compared to what thermal storage may offer.
In such a scenario it indeed make sense to convert generated electrical energy and store it as heat and then reuse it when necessary using engines, heat exchangers and electrical generators.
This set up is way more useful in cold environments where heat is necessary just to survive and wind is dominant renewable source available
This would be somewhere around 20% efficiency about the same as what solar is today.
Two important components for this to work and efficient external heat engine and a thermal energy storage device
Mechanical work
Some purely mechanical devices include fans ,coolers, AC, refrigerators, pumps ,Motors, engines, automobiles ,cooling ,heating, transport and pumping.
All of the devices performing mechanical work can be made using heat as the energy source and an engine as a transducer converting heat energy into mechanical work.
Advantage of this approach is that it simplifies the materials used for devices you don't then need conductive metals to make devices performing mechanical work .They can be made using polymers.
Additionally heat can be stored cheaply in large quantities for months on end making off grid approach far more feasible then electrical energy generation and storage.
More importantly instead of entirely replacing the grid, heat + engine combo can be used to tackle two most important requirements in a home /building: heating and cooling.
This helps us sustain the most energy demanding applications while reducing the burden on the grid and taking a big step forward towards sustainable energy use.
It is important to distinguish between purely electrical and purely mechanical work to understand what kind of energy input a device needs.
Most of the electro mechanical devices in use today are actually devices that do mechanical work but they just so happen to use electrical energy. The reason being that electrical energy can be transported to long distances making generation at a distant, more favorable, location possible.
This is great for connected systems like a city where a centralised generation facility can distribute energy to people's homes via grid.
Electricity transmits easily but is difficult to store.Batteries are expensive and complicated devices. More importantly though electricity is not really necessary to drive mechanical systems the only reason for its use is its ease of transmission.
On the other hand It's not only possible to concentrate energy directly from sunlight and store it but also store electrical energy as heat from wind,hydro sources ,if that heat will then be used to perform mechanical work.
Dividing the work into purely electrical & purely mechanical helps us make better use of energy that is available to us.
Could stored heat be used for cooking?
hot air cooktops perhaps?
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