Heat 2 Power:
New Thermo Storage Technology []

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:

The wrong form of energy is often in the wrong place at the wrong time. Why do we need heating energy in summer? How to replace energy from gas or nuclear power with electricity?
Renewable energy is unreliable. The performance of a wind turbine reacts very sensitively to changes in wind conditions, it changes with the 3rd power of the wind speed. In the case of a wind power plant, only around 15-20% of the nominal output is available on an annual average. This average value is not reached in around two thirds of the operating time.

Frequency distribution of the annual electricity production of a 3000 kW wind turbine:
number of days above the generated power in kW per day (3000 kW x 24h = 72000 kWh)
At the same time, we run the risk of massive overproduction.
Where does the electricity come from during a dark doldrums? Solar power and wind power contribute almost no guaranteed output. For the times without wind and solar power, you need additional power plants to step in to fill the gap.
It is a fatal mistake to believe that storage can still be delayed because other flexibility options (load management, flexible power plants) are even cheaper. The problem has already caught up with us with a considerably renewable electricity share. It just doesn't seem acute yet, since there are currently still enough (fossil) backup options and the little technologically open focus has so far been on expensive storage options (power-to-gas, batteries). Contrary viewpoints are based on old assumptions, such as that gas is cheap.
If you could store electricity, you would have high investment costs, but you save yourself the purchase and dependence on fuel.
Excess energy from peak performance currently has to be curtailed or dumped. It would be better to be able to store this electricity.

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:

The RE electricity production from solar energy and wind power varies greatly throughout the year. Solar energy dominates in summer and wind power in winter, so that the cumulative fluctuations in renewable electricity generation are distributed relatively evenly over the whole year. They mainly have a weekly (corresponding to the typical duration of a high or low pressure weather situation) and a daily rhythm (corresponding to the solar radiation).
The power requirement ("load") shows the greatest fluctuations in the weekly and daily rhythm. These are unmistakably larger than the seasonal ones. Fortunately, solar power generation peaks at times when demand is particularly high.
The difference between the power demanded in the power grid ("load") and the fluctuating feed-in from weather-dependent generators such as wind power or Photovoltaic systems (the white area below the load curve) is referred to as the residual load, which is caused by conventional systems or new construction of wind turbines and photovoltaic systems would have to be provided. This scenario applies for the most European countries.
If one day sufficient wind power or photovoltaic systems are available, the area that is still shown in white today could be filled with smoothed, i.e. temporarily stored, energy. This mainly affects the minima areas between the peaks.
To date, it is planned to fill this gap with gas-fired power plants. After the end of the expansion of wind power and solar systems, gas-fired power plants would only step in during dark periods. However, they would have to be dimensioned so large that they could replace the entire renewable energy generation.
But that also means you shouldn't boast about the installed total output. Everything that is generated above the average power belongs in storage to ensure a base load. The only relevant value is therefore the average power.
Objection: Isn't it cheaper to use all the electricity generated from renewable energy directly instead of storing some of it and using losses to generate electricity?
Answer: No! Because in the event of a dark doldrums or times with little electricity production, other power plants would have to step in. These would therefore have to be designed for very high outputs and the conversion losses would only be shifted from the reconversion of renewable energy to the gas-fired power plants. You have to maintain the Thermo Storages charged at all times. If they are empty, the demand for gas and gas power plant capacities during dark doldrums would be very high.
Overall, it would be better to have efficiencyoptimized base loadpower plants, beyond that renewable electricity production, which also has base loadcharacter due to smoothing and intermediate storage, and finally, for peak power only comparatively low base load power plant capacities. These could then be operated continuously and produce methane or hydrogen during times when there is sufficient EE production at the same time, in order to avoid downtimes in this way.

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.

The use of excess or peak power for producing methane leads to the effect that these plants have high downtimes and are not worth investing in. However, they would still have to be designed for large outputs or the peaks in electricity generation would have to be discarded.

The multiple conversion in the power-to-gas process also leads to high losses in the electricity originally used. An overall efficiency of less than 30% remains. It is often suggested that the poor levels of efficiency in the "Power-To-Gas-To-Power" process can be improved by using waste heat. It is ignored that this waste heat is not available for a large part of the year because these plants are idle for lack of excess wind.

Renewable energy	100%

transformer and rectifier (η = 95%)
	95%
electrolysis (η = ca. 75%)
	70 ... 72%
methanation (η = 80%)
	56 ... 60%
compressor, storage (η = 98%)
	55 ... 58%
Transport (η = 99%)
	55 ... 57%

Gas To Power: Gas and steam turbine, fuel cell (η = 50%)

Remaining energy 28 ... 29%

Gas To Power: Gas motor, Gas turbine (η = 35%)

Remaining energy 19 ... 20%

Combined heat and power generation to increase efficiency makes sense mainly in winter. Otherwise rather not. It is generally problematic to find consumers for heat in the vicinity of the plant. We therefore primarily need storage for electricity.
Processing into usable methanol or methane directly at the wind or solar system is almost impossible due to the high costs and complexity of the production systems. The methane would also have to be collected on site, that is, gas networks would have to be laid at every production site. Decentralized, regenerative generation also requires decentralized structures for storage and grid stabilization in the long term.
Even proponents of power-to-gas technology see the possibility that power-to-gas will become competitive from 2030 at the earliest.
Where does all the CO₂ needed for the methanation process come from when the fossil fuel power plants are shut down? This must also be included in the cost, energy and efficiency balance.
In addition, the power-to-gas plants are neither climate-friendly nor sustainable. Methane has a significantly stronger climate-damaging effect than carbon dioxide.

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.

Overall, the existing technologies for storing electricity are too expensive, too inefficient, resource-intensive and/or cannot be implemented on a large scale.
With "Power To Heat To Power" efficiencies of reconversion in a heat and power machine of up to 50% can be achieved.
Heat accumulators are not characterized by a particularly high energy storage density. Rather, their most important advantages are their low price, storage efficiency of around 90%, high cycle stability and resource frugality.
What is interesting about the technology is that existing solar (thermal) power plants or wind power plants can be retrofitted with heat storage for "power-to-heat-to-power" with manageable effort.
High-temperature storage is cost-effectively scalable.
The grids are not suitable for the strong fluctuations in volatile energy production. The fewer decentralized storage options are available, the more investments have to be made in the networks. This is only more cost-effective if you fixate on power-to-gas and battery storage.

"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?

Peak or excess power from regenerative energy production has not to be discarded anymore and can contribute to assure basic load.
The use of previously unused waste heat has also to be considered. This energy occur in large amounts in cement, glass and steel works, etc.
It must be used in the sense of climate protection and in view of the enormously increasing future demand for electricity. Since this heat often occurs only cyclically, the New Thermal Storage Technology is an adequate solution for smoothing.

What is special about the New Thermal Storage Technology?

The New Thermal Storage Technology eliminates various disadvantages of existing thermal storage systems, the functionality of which is limited to "heat in - heat out".
The New Thermal Storage Technology opens up the option of completely rethinking the energy transition. We are not dependent on batteries, hydrogen or methane and can guarantee energy security even during dark periods with manageable effort and costs.

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:

Not the highest quality storage material is the starting point of the design and then the system is constructed around it. The overall configuration and functionality is the basis for the storage material to be selected. As a result, only then a suitable storage material is selected and then the dimensions determined.
Charging and discharging are decoupled and each represents an independently operating system.
The system can only be optimized thermodynamically and fluidically if it works like a countercurrent heat exchanger.

Features and details of the New Thermo Storage Technology

Contact + request for licenses

Dipl. Ing. Thomas Seidenschnur
info@heat2power.com

Heat 2 Power: New Thermo Storage Technology []