Energy storage systems – the key to the energy revolution and global climate protection

Climate change is a reality. Every nation on our planet is affected by weather extremes, a rise in sea level or a scarcity of drinking water. Only joint action – which, after years of dispute, was finally agreed upon at the historic 2015 UN Climate Change Conference in Paris – and a global move to renewable energy resources can limit the consequences of global warming. Highly efficient energy storage systems are required, however, in order to use solar, wind and hydropower non-stop and all year round.

Up to now, the focus has tended to be on the direct storage of electricity by means of expensive batteries. However, batteries have only a short service life, are expensive due to their complex chemistry and can only be recycled with great difficulty. Yet energy can also be stored very efficiently as heat. When taken out of storage, this heat can not only be used for heating spaces, but can also be converted back to electricity at any time. In addition, thermal storage systems – such as those developed to marketability by EnergyNest – beat all battery options on a number of relevant points: they are cheaper and easier to produce, are longer lasting and environmentally friendly as well. Therefore, it is only logical to exploit the immense potential of thermal storage substantially more in the future.

Heat is valuable energy

Cosy warm flats, a hot cup of tea, glowing rivers of molten steel:

without heat – from pleasant room temperature to great heat – daily life and efficient industry would be unimaginable. We use this most popular form of energy without a second thought. But the potential of heat has so far been seriously underestimated. It often disappears as waste heat – completely unused. Thermal storage systems employing the special EnergyNest HEATCRETE concrete can change this. They are the key to more energy efficiency in the industry, more flexibility for wind and solar farm operators and for drastically reduced energy costs. This is because the stored heat can be reused as either heat or for power generation at efficiencies of more than 90 per cent. Thermal storage systems therefore simplify the global move towards a more climate-friendly energy supply.

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How do EnergyNest thermal storage systems work?

The fundamental principle of thermal storage is best demonstrated if we look at a summer beach. Until late in the evening, the sand – which is heated by the warmth of the sun during the day – releases its pleasant heat. This good heat uptake by solid substances also benefits the EnergyNest storage system. But instead of sand, it consists of a specially developed concrete mixture called HEATCRETE. Highly compressed and compact, the smooth marble-like material stores the heat much more efficiently: whereas a sandy beach has cooled down noticeably by the next morning, HEATCRETE loses a mere one per cent of its heat over the course of 24 hours.

Low losses such as these are valid for a broad temperature range from 50 to 550 degrees Celsius. Solar insolation simply cannot deliver this kind of heat. In an EnergyNest thermal storage system, a network of thin steel tubes runs through the HEATCRETE material. Hot steam or heated oil circulate through the tubes, transferring the heat and thus heating the special element. Anywhere from hours to days later, the heated thermal energy reservoir can be tapped into again using the same system of tubes. The material then transfers its stored heat to the cooler water, resulting in hot steam that is heated to several hundred degrees. If oil flows through the tubes instead of water, it remains liquid even at great heat. Both the hot steam and the heated oil allow efficient power generation via heat exchangers and turbines with efficiencies of up to 40 per cent. If the stored heat is also used for heating or industrial processes, the efficiency even increases to over 90 per cent. Whether a small system using only one module or large storage systems using dozens of modules are installed is not relevant at all.

HEATCRETE – not just simple concrete

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However, not every concrete mixture is suitable for this efficient thermal storage system. Years of research were required to develop the best formulation for HEATCRETE. The material needs to not only be capable of rapidly storing heat but also of holding it for long periods. In addition, the storage capacity or the quantity of heat – measured in kilowatt-hours similar to electricity – should be as high as possible; for example, a single HEATCRETE unit – weighing 75 tonnes and slightly smaller than a shipping container – has a capacity of 2,000 kilowatt-hours of heat.

The HEATCRETE response, when heated from a lukewarm 20 degrees to a tremendously hot 550 degrees, is astounding. Just like every other material, the special element expands; but it must expand and shrink again upon cooling to match the encased steel tubes as closely as possible. If this were not the case, cracks would soon appear in the special element – and a thermal storage system with cracks and a crumbling contact surface could not function reliably. The EnergyNest developers have met this challenge so well that the thermal storage system can be heated up and cooled again millions of times. It offers a very high service life of 50 years. It is no surprise, then, that this unique thermal storage system is globally protected against illegal reproduction by several patents.

Low maintenance, environmentally friendly, economical

No user needs to be afraid of the complex operation of EnergyNest thermal storage systems. They can be operated with only a small degree of manpower and a large degree of automation, since not much moves in the storage modules – apart from the circulating oil or steam. They require minimal servicing with their lack of complex mechanisms.

In addition to low operating costs, moreover, the user must initially invest less for the construction of EnergyNest storage systems because – at around 20 to 25 US dollars per kilowatt-hour storage capacity – they are available for less than complex storage systems that use batteries or other thermal storage systems on the basis of molten salt. Last but not least, EnergyNest storage systems can be produced almost anywhere in the world from locally available raw materials, such as quartz, in a largely (80 per cent) environmentally friendly and sustainable manner. The costly transportation of heavy modules over long distances thus becomes superfluous.