Low temperature waste heat recovery and utilization is an important energy-saving technology aimed at recovering and reusing low-temperature thermal energy (usually below 300 ℃) emitted from industrial production or other processes, in order to improve energy utilization efficiency and reduce energy waste. Here are some advanced energy-saving technologies for low-temperature waste heat recovery and utilization:
Organic Rankine Cycle (ORC)
ORC is a technology that utilizes low boiling point organic working fluids such as ammonia, fluorocarbons, or hydrocarbon compounds to convert low-temperature waste heat into electrical energy. It is suitable for waste heat sources ranging from 100 ℃ to 300 ℃ and is widely used for industrial waste heat, geothermal, and biomass power generation. Compared with traditional steam Rankine cycles, ORC has higher efficiency and more compact equipment under low temperature conditions.
Absorption refrigeration technology
This technology utilizes low-temperature waste heat to drive absorption refrigeration machines (such as lithium bromide absorption refrigeration machines), converting thermal energy into cooling capacity for use in refrigeration or air conditioning systems. It is particularly suitable for scenarios such as factories or data centers that require simultaneous heating and cooling needs.
Heat pump technology
Heat pumps use a small amount of electricity to elevate low-temperature waste heat to higher temperatures for heating or process heating. Common types include compression heat pumps and absorption heat pumps, with the latter being particularly suitable for utilizing low-temperature waste heat (such as 60 ℃ to 150 ℃) and widely used in industries such as chemical and food processing.
Thermoelectric Generation Technology
By utilizing the Seebeck Effect, thermal energy is directly converted into electrical energy through temperature differences. This technology is suitable for small, low-temperature waste heat recovery scenarios (such as automobile exhaust or small industrial equipment), with the advantages of no moving parts, simple maintenance, but relatively low efficiency.
Thermal Energy Storage Technology
By using phase change materials (PCM) or sensible heat storage materials (such as water, concrete) to store low-temperature waste heat and release thermal energy when needed. This technology can balance the time difference between energy supply and demand, and is suitable for the recovery of intermittent residual heat sources, such as solar thermal utilization or periodic heat dissipation in industrial production.
Optimization technology for heat exchangers
Advanced heat exchanger designs, such as microchannel heat exchangers and plate heat exchangers, can more efficiently capture and transfer low-temperature waste heat. These devices improve the efficiency of heat recovery by increasing the heat exchange area and optimizing fluid flow, and are commonly used for the recovery of flue gas waste heat or liquid waste heat.
Kalina Cycle
Karina cycle uses ammonia water mixture as working fluid, which has higher thermal efficiency in low-temperature waste heat power generation compared to ORC, especially suitable for waste heat sources with large temperature fluctuations. It has performed well in some geothermal and industrial waste heat power generation projects.
Direct utilization of low-temperature waste heat
Directly using low-temperature waste heat for preheating process media (such as preheating water, air) or district heating without the need for energy conversion. This method is simple and efficient, especially suitable for scenarios where the waste heat temperature is close to the required temperature.
The choice of these technologies usually depends on the temperature, flow rate, application scenarios, and economy of the waste heat. For example, ORC and Karina cycles are suitable for power generation, heat pumps and absorption refrigeration are suitable for temperature difference utilization, while thermal storage technology emphasizes the spatiotemporal matching of energy. In recent years, with the advancement of materials science and engineering design, these technologies have significantly improved efficiency and cost, promoting the widespread application of low-temperature waste heat recovery.