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.
The generic and vague wording of the question seems deliberate, but unfortunately a meaningful answer can't be so simple.
The primary factor that determines how long it will take a dryer to dry a load of clothes is not actually temperature, it's airflow. All the heat in the world won't help you if your dryer is overloaded, the lint tray is full/blocked, and ...
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 ...
Available data indicates that; 1) electricity usage for water pumping at homes is minimal; and 2) most municipal water systems provide more pressure than required for residential uses
Is it common for people on city water in the US to have their own on-site pumping as part of the "standard" delivery system?
The U.S. Energy Information Agency's 2015 ...
Nutshell answer: Residential use: nil.
Commercial use: Significant. Any reasonably large building has a larger problem getting rid of extra heat compared to heating. All those lights and photo-copiers add up.
Many commercial buildings and large facilities like University campuses will buy power when it's cheap at night and use it to chill water or brine. ...
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;
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.
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 ...
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. All so-called "renewables" (a misnomer) actually use fusion energy from the sun. The sun has a finite life. If we could find a terrestrial non-intermittent power source that lasts for 5 billion years ...
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 ...
The proton.energy website is very optimistic, maybe a bit too much. I see a number of (potential) problems:
The technology uses "hydrocarbon reservoirs" which is a different word for existing oil and gas fields, so that makes the resulting fuel non-renewable.
The exact process is not clear to me, but the paper they link to talks about water being ...
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 ...