General Manager
Sven-Olaf Klüe has been working in the field of design, manufacture and applications of pillow plate heat exchangers worldwide for 27 years. For the past 15 years, he has focused specifically on the process-related applications of pillow plate heat exchangers in industrial applications.
Industrial ice storage in combination with photovoltaics
The key to energy saving by thermal energy storage
Introduction
Photovoltaic systems have the disadvantage of not directly adapting their electricity production to the demand. This often results in insufficient power during peak times and excess power during low-demand periods. Consequently, surplus electricity needs to be fed into the grid at low compensation rates during the day if no suitable measures are taken. Conversely, grid electricity needs to be purchased at night when the photovoltaic systems generate little to no power. This can have a negative impact on the profitability of a photovoltaic system.
Furthermore, photovoltaic systems increasingly burden the power grid through their feed-in. Thermal energy storage systems provide a good opportunity to address these challenges. Battery storage is the most commonly known solution, but their production still incurs high costs and significant environmental impact.
The energy turnaround and the expansion of renewable energies are topics that are particularly relevant in industry. One innovative way to save energy and switch to renewable energy sources at the same time is to use an ice bank in combination with photovoltaics. This advanced technology is already used in many industries and offers numerous benefits, including higher efficiency and better control over energy consumption. By adopting industrial ice storage, companies can not only reduce their costs, but also take an important step towards implementing the energy transition and reducing their environmental footprint.
Explanation of the individual thermal energy storage components
What are industrial ice banks? What is thermal energy storage?
The cold storage system is based on a conventional booster concept with heat utilization. Typically, an ice bank with a separate evaporator is used. The ice bank is connected to the refrigerant circuit via a water-glycol intermediate circuit. In the event of excess power from the photovoltaic system, the ice bank is cooled in addition to the regular cooling load, which is referred to as the charging process. Refrigerant components are extracted before the medium-pressure collector and expanded into the evaporator of the ice bank. The intermediate circuit with water-glycol mixture as well as the ice bank itself are cooled in the process. Additional compressors provide the charging energy. This allows the ice bank to be charged even at full system load.
If the photovoltaic system produces less electricity than needed, the ice bank is discharged to support the cooling system. This enables the cooling system to operate more efficiently and consume less grid electricity for the same cooling load. The electricity stored during the day by the photovoltaic system is retrieved during peak times and during the night to match the needs of photovoltaic production.
It is advisable to carry out a cost calculation and a life cycle analysis between ice banks and battery storage for each project, as ice banks are still cheaper than lithium-ion batteries with the same storage capacity. The production of ice banks causes lower environmental impact and significantly lower greenhouse gas emissions compared to the production of new batteries. The storage capacity of batteries decreases steadily over their lifetime. However, it should be noted that both ice banks and batteries are assumed to have a lifespan of 15 years, which corresponds to the lifespan of the cooling system. It is very likely that second-life batteries will need to be replaced multiple times during this period, while an ice bank can often be operated for well over 15 years.
Industrial ice banks are a type of energy storage used in industry to store surplus energy and release it when needed. They work on the principle of latent heat storage, where energy is stored in the form of solidifying ice and released by melting ice.
The evaporator plates are crucial for successful ice production. They are placed upright in a water tank, which can be either rectangular or round. An evaporation temperature between -4 and -10 °C is used to form the ice, which sticks to the plates, forming a static ice bank. To ensure uniform thawing, a distribution system for the warmer return water is installed on the bottom of the tank. In addition, an automatic distribution system for air circulation ensures perfect heat transfer, keeping the temperatures of the ice water low and creating intensive turbulence. This only occurs when required and ensures optimum ice production.
Maximum cooling capacity at the lowest ice water temperatures is ensured by an almost constant ice surface until the end of the cooling phase.
When energy is needed, the ice is melted. The energy storage in the form of heat is released and can be used to cool process water, production facilities or even rooms. In times of low energy demand from the grid, cooling energy is generated by a refrigeration system and fed into the ice storage. During peak times from the grid, this thermal stored energy can then be used to provide the required cooling capacity without having to restart the refrigeration unit.
Advantages of industrial ice banks
What needs to be done to accelerate thermal energy storage?
An ice storage system offers numerous advantages for companies and plants that require high cooling capacities during peak loads. This is because by using an ice storage system, smaller chillers can be used that are designed for average demand. The result: a higher cooling capacity at lower costs. This is because the ice storage enables the use of favourable electricity tariffs, which can be up to half of the normal electricity price. In addition, the base price for electricity can also be reduced because the maximum electricity peaks are limited. This cost efficiency can be crucial for companies that want to reduce their large thermal energy costs without having to sacrifice high cooling capacity.
Ice storage is a promising means of increasing energy efficiency. Due to their high efficiency, they minimise the energy losses that can occur when storing energy in other systems such as batteries. In addition, they can provide energy quickly, which is particularly important in industry. Ice storage systems are particularly durable and require little maintenance. Another advantage is that they work independently of the outside temperature, which means they can be used in cold regions. By using ice storage, energy costs can be reduced by up to 40 percent, which contributes to energy savings and cost efficiency.
Photovoltaics as renewable energy: What is it?
Photovoltaics is the conversion of solar energy into electrical energy. It uses solar cells, which are made of semiconductor materials and convert sunlight into electricity. Photovoltaics is a sustainable energy source because it produces no harmful emissions, is inexhaustible and therefore one of the renewable technologies.
Advantages of photovoltaics
Photovoltaics is a resource-saving and environmentally friendly energy source that offers many advantages. One of the most important features is its sustainability, as it does not cause CO2 emissions. By using photovoltaics, one can become independent of fossil fuels and thus use energy at stable prices. Another advantage is the enormous flexibility of the technology - it can be used in any place with sunlight. Best of all, the running costs are very low, making the use of photovoltaics even more attractive. If you are looking for a cost-efficient and environmentally friendly source of energy, photovoltaics is a great solution and one of the green technologies.
Combination of industrial ice banks and photovoltaics
How does the combination of industrial ice banks with photovoltaics in form of solar panels work? Using favourable electricity tariffs and avoiding peak loads for cooling with ice storage?
The combination of industrial ice banks with photovoltaics offers an effective solution for using renewable energies in industry and saving energy. Feeding the electricity from the photovoltaic systems directly into the ice storage systems contributes to the sustainable coverage of demand. Especially during sunny hours, the electricity supply from the photovoltaic systems is used to form the ice inside the stainless steel tank, further reducing the energy demand. The combination of industrial ice banks with photovoltaics is an exemplary model for the effective and sustainable use of energy in industry.
In the midst of advancing technology, it is safe to say that we are moving towards energy efficiency. Photovoltaic systems are undoubtedly among the leaders of this movement. Their biggest advantage is the direct delivery of electricity, which can eliminate the loss of electricity during transport. Another innovative use is the storage of energy that can be used at night to maintain material production. This energy is stored in the ice bank tanks and used when necessary to cool processes, buildings or machinery. Integrating photovoltaic systems and ice storage in one system not only increases energy efficiency, but also reduces dependence on the normal power supply.
What are the advantages of combining industrial ice storage with photovoltaics?
Why do we need thermal energy storage?
Photovoltaics is a way to generate renewable energy by converting solar energy into electricity. When photovoltaics are combined with industrial ice storage, the advantages are as follows:
- Energy cost reduction: Photovoltaics solar energy usually generate more energy than is needed in the immediate vicinity. By combining it with thermal ice storage, this excess energy can be stored and used later for processes in plants to reduce thermal energy costs.
- Increasing energy efficiency: Industrial ice bank systems can store energy very effectively and release it later. When combined with photovoltaics solar energy, the entire energy production and use can be made more efficient.
- Sustainability: The combination of renewable energy from photovoltaics and the thermal energy storage in ice reservoirs is a sustainable solution for industry. It contributes to the reduction of CO2 emissions and thus to large environmental protection as renewable energy. In addition, the use of thermal ice storage and photovoltaics can help to reduce dependence on fossil fuels and thus increase security of supply in the long term.
Conclusion
It is possible to incorporate an ice storage system into a direct-expansion booster refrigeration system and operate it. During the charging process, the excess photovoltaic output increases the power consumption of the refrigeration system, thereby increasing self-consumption and relieving the power grid by reducing feed-in. Unfortunately, in most cases, this does not significantly affect the self-consumption share. This is usually due to a powerful photovoltaic system that produces significantly more electricity during the day than is needed. At maximum charging power and full photovoltaic production load, only a portion of the excess photovoltaic energy can be absorbed.
During the day, the refrigeration system is relatively inefficient due to higher outdoor temperatures and is subject to increased stress when the ice storage system is being charged. At night, the refrigeration system operates much more efficiently due to lower outdoor temperatures. Since the ice storage system provides thermal support, the higher efficiency during the night reduces electricity consumption savings. The lower the outdoor temperature, the higher the efficiency of the refrigeration system, the lower the savings in grid electricity, and the less potential for undercooling due to the ice storage system. The cooling demand, the efficiency of the system during discharge, and the average outdoor temperature significantly determine the size of the ice storage system. Therefore, there are also limits on the size of the photovoltaic system to utilize the storage concept to increase self-consumption share.
For industrial companies that need a reliable and efficient energy supply, the combination of ice banks and photovoltaics is an ideal solution. By harnessing renewable energy and being able to store and use energy efficiently, companies can achieve significant cost savings and meet their sustainability goals. As technology advances and interest in renewable energy increases, this combination of ice banks and photovoltaics is sure to play an increasingly important role in industrial energy supply. Companies looking for a future-proof energy supply should consider this innovative technology.
Finally, we would like to point out that solar thermal collectors are much more efficient with an efficiency rate of 80%, compared to photovoltaic modules with an efficiency rate of only 14 to 22%. With a solar heat system, you will require less surface area and benefit from a clear advantage over photovoltaics.