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The Limitations and Inefficiencies of Thermal Energy Storage for Electricity Generation


Core Concepts
Thermal energy storage systems, such as using vertical tanks filled with salt, have significant limitations in their ability to efficiently convert stored heat into usable electricity, with average round-trip efficiencies of only around 10%.
Abstract
The article discusses the limitations and inefficiencies of using thermal energy storage systems, such as vertical tanks filled with salt, to store heat and then convert it back into electricity. The author provides a detailed analysis of the underlying thermodynamics and the practical challenges involved. Key highlights: Using Carnot's formula, the theoretical maximum efficiency of converting the stored heat into electricity in a 20°C environment is only 62%. The rest is lost as waste heat. As the thermal storage medium cools down during discharge, the temperature difference between the storage and the environment decreases, leading to a further drop in efficiency. At 30°C, the efficiency can be as low as 3%. Accounting for real-world energy losses during conversion and power generation, the average round-trip efficiency of such a thermal energy storage system is estimated to be around 10%, resulting in a 90% energy loss. The author argues that this poor efficiency is one of the reasons why concentrated solar power stations, like the Ivanpah Solar Power Facility, have failed to become a viable solution to the energy predicament. The author also discusses the broader context of the increasing energy cost of energy, where the efficiency of the entire industrial civilization is declining as the fossil fuel industry taps into lower-quality reserves. The author suggests that thermal storage could be more practical for residential and small-scale commercial use, such as for heating, hot water, or process heat, but not for large-scale electricity generation.
Stats
Theoretical maximum efficiency of converting stored heat into electricity in a 20°C environment: 62% Efficiency at 250°C inner temperature: 44% Efficiency at 30°C inner temperature: 3% Estimated average round-trip efficiency of a thermal energy storage system: 10%
Quotes
"Without going too much into the details, the limiting factors of such a system are the temperature at which the heat enters the engine, and the temperature of the environment into which the engine exhausts its waste heat." "Adding insult to injury heat also tends to dissipate during storage, or the time spent between "loading" the heat battery and "discharging" it. (Oh, that damned second law of thermodynamics, again…)" "Folks, we are talking about a 90% energy loss here... How come this "idea" hasn't received a Nobel-prize yet…?"

Key Insights Distilled From

by at thehonestsorcerer.medium... 04-15-2024

https://thehonestsorcerer.medium.com/thermal-storage-hopium-7166dc6f8aa1
Thermal Storage Hopium

Deeper Inquiries

What alternative energy storage technologies could potentially overcome the limitations of thermal energy storage systems and achieve higher round-trip efficiencies?

One alternative energy storage technology that could potentially overcome the limitations of thermal energy storage systems is advanced battery storage, such as lithium-ion batteries. These batteries have higher round-trip efficiencies compared to thermal storage systems and can store electricity more efficiently. Additionally, flow batteries, compressed air energy storage, and flywheel energy storage systems are also promising alternatives that can provide higher efficiencies and better energy storage capabilities.

How can the increasing energy cost of energy be addressed in a sustainable manner, beyond the reliance on thermal or other energy storage solutions?

To address the increasing energy cost of energy in a sustainable manner, it is essential to focus on energy conservation and efficiency measures. This includes improving the efficiency of energy production processes, reducing energy waste in industrial and residential sectors, and promoting energy-efficient technologies. Additionally, investing in renewable energy sources with high energy return on energy invested (EROEI) values, such as solar and wind power, can help reduce the overall energy cost of energy production.

What role could small-scale, decentralized thermal energy systems play in the transition towards a more sustainable energy future, and how can their adoption be encouraged?

Small-scale, decentralized thermal energy systems can play a significant role in the transition towards a more sustainable energy future by providing localized heating, hot water, and process heat solutions. These systems can reduce the reliance on centralized energy production and distribution, leading to lower energy losses and increased energy efficiency. To encourage their adoption, policies and incentives can be implemented to promote the installation of small-scale thermal energy systems in residential and commercial buildings. Additionally, raising awareness about the benefits of decentralized thermal energy systems and providing technical support for their implementation can help accelerate their adoption.
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