Engineering Toolbox gives the specific heat capacity of rock as 0.84 kJ/kg.K.
Let's work with 40 TJ = 4 × 1013 J = 4 × 1010 kJ.
Let's say we could operate with rock starting at 600°C and ending at 200°C so a ΔT of 400°C through the heat extraction cycle.
From the SHC we can calculate
At 3 T/m3 that gives a volume of
That's a cube of 34 m side.
By order of magnitude your approximation is reasonable. I compared it to a 2021 analysis performed by Mark Jacobson as part of his 100% Wind, Water, and Solar (WWS) All-Sector Energy Roadmaps for Countries, States, Cities, and Towns. The results for Italy are available here (pdf).
For a complete electrification of the transport sector by 2050, Table 2 shows ...
Get your coffee beans with rainforest alliance certification
Drink it black or with non-dairy whiteners
I think the points you mention are relatively trivial compared to the big things:
Where the coffee comes from and how it is transported
If you add milk
Professor Mark Maslin and PhD student Carmen Nab have analysed the environmental ...
How do you propose capturing methane laden cow burps?
Land fill sites are stationary and inanimate. Getting methane out of a land fill site basically involves putting some pipes into the back fill site and running the pipes to a central collection point to process the gas. Some pumping of the gas may be required.
Cattle however, are live mobile creatures. ...
It's the timescale that's the issue.
Firewood is generally harvested from a managed forest; there's a continuous cycle of planting, harvesting, and burning going on, and the carbon dioxide released from this year's burning will be absorbed in next year's growing season.
Major forest fires are not continuous events. Even with a healthy fire cycle going on, ...
There are very many ways energy can be sustainable and reliable at the same time.
Firstly, you can observe the fact that there is no renewable energy. Most so-called "renewables" (a misnomer) actually use fusion energy from the sun, although some less common "renewables" like geothermal power or tidal power use other finite sources of ...
If you want to include a means of energy storage within the system then yes.
Batteries can be used to store electrical energy for when the sun doesn't shine and when the wind doesn't blow, when the tide is not moving in tidal systems or when waves are flat in wave energy system.
Solar or wind powered pumps can be used to return water to hydroelectric dams.
Depending on where the houses are located; in the Mid-West USA, flat ground and raised water towers means most of the water is gravity fed (with only the initial pumping to get the water into the tank).
In my city (Southern California, USA) approximately 40% of our water is gravity fed, the remaining 60% has pump that feed and fill tanks upon the hill, which ...
Energy payback in 1-6 years
Taking manufacturing variables into account basically gives you a range of time from 1.25 - 6.5 years based on 5 sunny days out of seven and an average of 6-8 hours of sun per day.
But in reality none of this matters, here’s why...
Fossil fuels never reach energy payback
Electricity as a commodity has been in use for over a ...
If the "embodied energy" of photo-voltaic tech is
~585kWh/m^2 and it generates ~0.2 kW/m^2 then;
the answer to the question seems to be that the photo-voltaic tech will need to run for:
= 2925 hours to generate it's embodied energy;
In my country, a typical motorist drives 15000 km/year. With state of the art electric cars that consume less than 0.2 kWh / km, and taking into account charging losses (that bring the total consumption from the grid to about 0.2 kWh/km), that's about 3000 kWh/year for a single passenger car.
The world produces 25600 TWh/year of electricity and has about 1 ...
No this won't work, because there's so much coal reserves, unless you buy all of them.
With oil it might just work. Buy an oilfield and promise to not utilize it in any manner. However, the fossil fuel industry is probably capable of finding more oilfields than there is room for carbon dioxide in the atmosphere, and electric car transition is rapidly ...
Abandoned underground coal mines present a potential hazard to anyone who might enter them. The first hazard is fugitive methane gas and the second is coal dust. Under the right conditions, both can be explosive.
Because of fugitive methane emissions it would be best for underground coal mines to be allowed to flood and to be sealed to prevent entry to the ...
Another thing to consider:
If burning wood for energy, it is generally displacing other alternative dirty fuels that would emit net carbon dioxide. However, forest fires do not displace anything. It's far better to harvest wood from forests and use it for useful purposes and replant a new forest than let a forest burn and replant a new forest.
However, for ...
If we compare the cost of solar/wind renewables vs fossil fuels, both Without subsidies, what is cheaper?
You have to understand the different roles of different power sources.
Coal is old-fashioned and dying. Traditional coal power plants have poor thermal efficiency, and alternatives such as integrated gasification combined cycle are expensive. Coal has ...
I tested this with two identical loads of laundry, mostly socks (so, plenty of retained moisture after the spin cycle). I then checked my smart meter's records of how much power was used during that period, and subtracted the "baseline" usage.
Tumble dry high: estimated 2.0 kWh, elapsed time 48 minutes
Tumble dry low: estimated 1.4 kWh, elapsed ...