Exactly! You're right Professor Alok Dhaundiyal. But the question is how much renewable energy is the best energy for nature.

Dear Sir,

Most of RE technologies can consider it as green energy source in compare with the conventional technologies which are used the fossil fuel to produce the required of energy and the criteria if its green is the total emission of GHG, the cost of RE technologies go down sharply now for example the LCOE of PV Solar Energy not exceed than 2 cent dollar per kWh while the price for conventional fuel not less than 4 cent dollar.

When these plants are in operation then they are green. On the basis of material the story is same for all.

I think green energy is green because of small quantity. If the energy is widely applied with large amoun of quantity, it will be not green any more.

Solar PV works out to about 50g of CO2 per kWh compared to coal's 975g of CO2 per kWh, or about 20x "cleaner." But we have to consider what will happen after 30 years.. recycling these panels will be a complex process with negative environmental impacts.

"Green " is an extremely unclear and ambiguous word. As a member of the physicist community, I do prefer using the words " low carbon process" i.e. concerning electricity generation. In which case it is important to specify the primary energy in use by the "solar equipment" manufacturing process. As it is certainly electricity, the way that one is itself generated is a key specification : everybody knows that when generated by a nuclear-fueled or coal-fueled power plant, the resulting kWh carbon intensity is respectively about 30 g or 975 g.

Then before stating any PV cell as a "so-called green" one, there are two questions :

(1) How many kWh enter in its construction, delivery, installation and end-of-life process

(2) What is the carbon intensity of related kWh.

Now my concluding remark :

To-day, renewables are positively regarded, a state-of-the art quite opposite to what it was more than 50 years ago when I have been graduated. That makes me quite happy. Then, may I suggest not to regard them from an ideologist viewpoint, better identifying each "Renewable", and more generally energy, case-study uniquely through cost-to-benefit (including energy efficiency and environment safety) ratio, in other words an authentic scientific way.

Best regards to all readers

Jacques

Dear Professor Jacques Roturier,

I agree with your words "better identifying each "Renewable", and more generally energy, case-study uniquely through cost-to-benefit (including energy efficiency and environment safety) ratio, in other words an authentic scientific way".

In terms of harmful emissions into the air, these technologies are certainly progressive.

But I think renewable energy technologies are polluting too much of nature (especially the rivers around which factories are built). But it should be borne in mind that the oldest generation solar panels are already installed - they are of extremely low efficiency. It is time to dismantle them and replace them with new, more efficient ones. But this will further worsen the environmental picture. Research shows that solar panels installed over vast areas somehow alter the local climate of the locations where they are installed.

And all this, given that nuclear energy has long been discovered. And its effectiveness is indisputable. It remains to find a suitable way to store and accumulate nuclear waste. Better yet, if technologies are created to neutralize nuclear waste - to turn it into safe materials.

Best regards to all readers

Anton Georgiev

Exactly! You're right Professor Alok Dhaundiyal. But the question is how much renewable energy is the best energy for nature.

yes.

absolutely no, but relative to old resources ,yes

No green energy! There are polluting technologies to varying degrees.

Unfortunately, the green energy isn´t green enough. Even reducing one nocive factor, we activate another.

E.g. The extensive use of solar energy will cause landscape interventionhs and the use of toxic materials. Yet the wind energy will kill birds, as their migration routs depend on the windrose.

Hydrogen and lithium energy requires extention on rare-earth mining, which pollutes the atmosphere. Moreover, the rare elements are about to be consumed, which will pose in question the mine regeneration.

So... we have to think, whether the "green" energy is really "green" or not.

Hi Anton/All,

I think the fundamental issue is the total solar energy input is huge (untapped) but how we capture it is what we are discussing. It is fair to say that living things have evolved a system on earth, were the components of it's structure can be recovered. Toxic material are trapped as insoluble compounds or released into the atmosphere.

Fossil fuels were the easy way of accessing trapped carbon and therefore the trapped energy in chemical bonds. However, they generated greenhouse gases. Our current problems are generated by an ever increasing population, a destruction of living things in terms of quantity and diversity and release of pollution as a consequence of releasing this trapped energy by combustion processes.

The challenge is really to develop more living systems within our modern world, also to use less resources and control population growth. In terms of renewable energy, the issue is the embedded resources/energy in the infrastructures. A lot of the technological solutions we are adopting are not renewable because they are made and rely upon metals and other materials that require to be concentrated and use high energy requirements to obtain them from the environment. We never build in recover/reuse either in the same or different application. This is our single use mentality, see attached for a new way of thinking about waste.

Biological systems, take the complicated spend living structure apart and use the embedded energy to build new and different structures. So the challenge is to have components that can be dissembled and reassembled into a multitude of different forms. In my opinion these will need to be organic, but like enzymes, they can incorporated the special properties for redox etc that metal have, when held in the right special position. We could envisage other structural assemblies from silicate systems.

I suggest that the real way forward to to engineer a new biology with the built in possibility of renewal and recovery. A big ask - but it will then address the fundamentals.

Otherwise, we need to harness energy with nuclear breakdown or fusion both of which are also problematic.

No answer - sorry, just re framed your question.

Actually not.