In the beginning was the fire

Heat is the oldest form of energy used by humans. Our ancestors kept a naturally occurring fire alive as a campfire. Today we have solved this problem, but there are new challenges:

How do we keep excess electricity from renewable energy generation alive?

First you have to be aware that there is (excess) electricity that needs to be stored. If the energy transition is to succeed, we not only need an incredible amount more electricity than we do now, we need this electricity to be available evenly and reliably. No one is helped by simply increasing the installed total nominal power. In the worst case, the high volatility of renewable energies leads to the so-called dark doldrums. Even in a large-scale network with a large number of wind power plants, there is a power curve with extreme fluctuations. That's why we need energy storage to smooth the performance and to deliver as needed.

The need for energy storage

Why does it have to be possible to store electricity from solar and wind power plants, even though their share of total energy generation is still comparatively small? The strong fluctuations in renewable energy generation cause several problems at the same time:

Conclusion 1: In order to be able to counteract excess electricity, there are three possible scenarios:
  • Extreme case 1: No storage capacity available. In this case, a large part of the fluctuating renewable generation would have to be curtailed.
  • Extreme case 2: No curtailment. The proportion of fluctuating RE generation would then be lower. In addition, enormous storage capacities would be required to absorb temporary excess electricity.
  • A combination of storage expansion, flexible load management, curtailment, generation of H2 and methane(ol) and flexible use of electricity in the heating sector. This would be the economically best compromise.
There are also three scenarios to counteract a power shortage during dark periods:
  • Extreme case 1: back-up power plants are required to compensate for the total volatile renewable energy generation that has failed.
  • Extreme case 2: Electricity storage systems are required to compensate for the total loss of volatile renewable energy generation for the duration of the dark doldrums.
  • A combination of flexible power plants, flexible load management and storage. This would be the economically best compromise.



Advantages and disadvantages of energy storage

Classic storage technologies are often too costly or resource-intensive for many applications or cannot be implemented on a large scale. The most common memory technologies:

Pump Storage Plants

Percentage of power supply from pump storage plants:

England: 0.4% (2021), Switzerland: 5.7% (2010), USA: 2.2% (2021), Sweden: 43.3% (2022), Austria: 9.8% (2021), France: 12.5% (2019), Norway: 96.3% (2019).

  • Suitable for long-term storage
  • High efficiency, efficiency 70 .... 80 percent.
  • In most countries, there are hardly any suitable locations left. A power plant means a massive, irreparable intervention in the landscape.

Batteries

  • Some types suitable for long-term storage
  • High efficiency
  • Limited lifetime
  • High performance rates of change
  • Capacity limited
  • Very expensive on a large scale or as a decentralized solution (swarm power plants)

Power-to-Gas

H2 or methane is generated by means of electrolysis.
  • Suitable for long-term storage. The existing natural gas network can store significant amounts here.
  • Costs between 2,500 and 3,500 euros per kilowatt of electrical output, depending on the size of the system.
  • Very low efficiency, high manufacturing losses. Approx. 3.5kWh of electricity must be fed into the methanation process for every kilowatt hour converted back into electricity.

Flywheel Accumulator

With flywheels, excess electrical energy is stored as rotational energy
  • Unsuitable for long­storage, idle losses of approx. 20% per hour
  • Very high efficiency
  • Very short response time
  • When a conventional power plant is shut down, its turbine and generator rotors are the first energy storage systems in the grid.

What kind of energy storage do we really need?

The discussion about the energy transition and storage technologies is mostly about buffer (or short-term) storage and long-term storage, so-called seasonal storage.

Due to a lack of electricity storage, efforts are being made to use CHP (combined heat and power). There is hardly any openness to technology and it is being pretended that the success of the energy transition primarily depends on the availability of battery and methane storage. Is it really like that?

The Golden middle

The following graphics make it clear that there is no need for high capacities of long-term storage, but for medium-term storage:



Renewable electricity generation and consumption for 2021, illustrating weekly and seasonal variations.



Renewable electricity generation and consumption over 10 days, for example in April 2022 in Germany, to illustrate daily fluctuations.


Hydropower  Photovoltaics  Bio mass 
Wind Onshore  Wind Offshore  Load history

The horizontal dashed lines show from top to bottom:
1. Maximum power, 2. Average power, 3. Base load (secured minimum power).

(https://www.agora-energiewende.de)

The illustrations clarify the following: For information: Base load power plants (e.g. gas and steam power plants) for maximum performance from nuclear power or coal achieve efficiencies of around 50%. Rapidly saturating peak load power plants with gas turbines only achieve 25...30% efficiency. New multi-cylinder hot gas engine systems with up to 15,000 kW achieve around 50% efficiency.

Conclusion 2: We don't need storage to save the electricity from July to January. We need storage to save power from Monday to Sunday and from afternoon to morning.

The aim of intermediate storage/smoothing of energy is that the secured minimum power is raised to the level of the average power and the peak powers fed in are reduced accordingly.

International Plans for the Energy Transition

How is the current situation? How should energy be made available during dark doldrums?

England:

The UK aims to achieve net-zero greenhouse gas emissions by 2050 and increase the share of renewable energy in its electricity mix to 40% by 2030. In 2020, renewable energy accounted for 43% of the UK’s electricity generation, surpassing fossil fuels for the first time.

The UK relies on a mix of flexible power plants, interconnectors with other countries, demand-side response, and energy storage to balance the grid during dark doldrums. The UK also plans to increase its pumped storage capacity and invest in new technologies such as hydrogen and carbon capture.

Switzerland:

Switzerland plans to phase out nuclear power by 2034 and increase the share of renewable energy in its electricity mix to at least 50% by 2035. In 2019, renewable energy accounted for 62% of Switzerland’s electricity generation, mainly from hydropower.

Switzerland relies on its large hydropower capacity and interconnectors with neighboring countries to balance the grid during dark doldrums. Switzerland also plans to increase its solar and wind power capacity and invest in new technologies such as batteries and power-to-gas.

USA:

The USA aims to achieve a carbon-free electricity sector by 2035 and net-zero greenhouse gas emissions by 2050. In 2020, renewable energy accounted for 20% of the USA’s electricity generation, mainly from hydropower and wind.

The USA relies on a mix of flexible power plants, transmission lines, demand-side response, and energy storage to balance the grid during dark doldrums. The USA also plans to increase its pumped storage capacity and invest in new technologies such as hydrogen and carbon capture.

Sweden:

Sweden aims to achieve 100% renewable electricity production by 2040 and net-zero greenhouse gas emissions by 2045. In 2019, renewable energy accounted for 57% of Sweden’s electricity generation, mainly from hydropower and nuclear power.

Sweden relies on its large hydropower and nuclear power capacity and interconnectors with neighboring countries to balance the grid during dark doldrums. Sweden also plans to increase its solar and wind power capacity and invest in new technologies such as batteries and power-to-gas.

Austria:

Austria aims to achieve 100% renewable electricity production by 2030 and net-zero greenhouse gas emissions by 2040. In 2019, renewable energy accounted for 75% of Austria’s electricity generation, mainly from hydropower and wind.

Austria relies on its large hydropower capacity and interconnectors with neighboring countries to balance the grid during dark doldrums. Austria also plans to increase its solar and wind power capacity and invest in new technologies such as batteries and power-to-gas.

France:

France aims to reduce its reliance on nuclear power from 75% to 50% by 2035 and increase the share of renewable energy in its electricity mix to 40% by 2030. In 2019, renewable energy accounted for 23% of France’s electricity generation, mainly from hydropower and nuclear power.

France relies on its large nuclear power capacity and interconnectors with neighboring countries to balance the grid during dark doldrums. France also plans to increase its solar and wind power capacity and invest in new technologies such as batteries and hydrogen.

Power-To-Gas is not a solution

The following considerations show why the frequently favored methanation is completely unsuitable for intermediate storage and smoothing of energy.
Conclusion 3: "Power-To-Gas" is only needed for long-lasting dark doldrums. To ensure a base load by means of methanation, systems that would have to bridge the difference from the base load to the peak power of the renewable energy source (provided that the existing gas network can absorb all the reserves generated) are needed.

How "Power-To-Heat-To-Power" works

A solar plant or wind turbine generates electricity. Power above a base load to be defined is converted into heat by a resistance heater ("Power To Heat") and transferred to an air flow. This heat is fed into a storage tank and removed from there at a later time and as required. The extracted heat is used to operate a heat engine ("Heat To Power") and is converted back into electricity.



Another option is to use industrial waste heat as energy source. Waste heat often occurs only cyclically or fluctuating and was therefore only partially suitable for reconversion.

Why "Power-To-Heat-To-Power"?

As described above, the methanation of electricity must be viewed critically. Methanation is not needed for the energy transition, it is also highly inefficient. No matter how much excess power is generated: Only with "Power to Heat to Power" it will be possible not to waste excess electricity, but to make it usable again in the future as needed. "Power-to-heat" has so far been a synonym for the utilization of electrical energy in the heating sector. By using electricity from renewable energies, "Power-To-Heat" systems represent an important building block for the decarbonization of the heating sector.
But now it's all about converting heat back into electricity: Power to Heat to Power.

Conclusion 4: In order to counteract long-lasting dark doldrums, we need storage that can store the average power (base load) for several days.

A 1,000 kW wind turbine (24,000 kWh per day) has an average output of approx. 150 kW (3,600 kWh per day). For every 1,000 kW of installed power, a storage tank of 7,200kWh is needed per day to be bridged. With a nominal output of 5,000 kW, that would be around 36,000 kWh per day.

Rule of thumb: 1 kW of installed nominal power x 7 = required storage size in usable kWh per day


Conclusion 5: The reconversion is best done in a system that is fed by thermal storage tanks, and can also be operated with gas.


Should the New Thermal Storage Technology be used in private households to generate electricity?

No. In the future, private households will store electricity using batteries or H2. Hot water tanks, on the other hand, are not suitable for generating electricity. The New thermal storage technology is intended for significantly greater performance, for securing the base load of the public grid.

What are the fields of application of the New Thermal Storage Technology?

What is special about the New Thermal Storage Technology?

The principles of the New Thermo Storage Technology

"If an idea doesn't sound absurd at first, then there's no hope for it" (A. Einstein)

The New Thermo Storage Technology follows the same principle as conventional storage systems, but the configuration of the entire system has been drastically changed. It is based on the following principles:

Features and details of the  New Thermo Storage Technology

Contact + request for licenses

  • Dipl. Ing. Thomas Seidenschnur
  • info@heat2power.com

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