Waste Heat Recovery – Automotive Industry in need of Knowledge Transfer
After regenerative braking, the mechanism which helps to store and reuse the kinetic energy extracted from brake application, the industry is looking forward to reusing ambient energy. There is a need to employ a system which recovers waste heat and converts it into useful energy. In case of electric vehicles, this will further help increase the range, whereas, in the conventional ICE vehicles, it will help reduce greenhouse gas emissions as well as improve performance.
In both developed and developing countries, energy efficiency and use of waste heat are increasingly gaining traction. The high emission of carbon dioxide (CO2) associated with automobiles raises serious concerns about environmental sustainability. According to the International Energy Agency, the number of vehicles in the world will double by 2040. New regulations are being imposed by the governments to reduce greenhouse emissions from automobiles. This has compelled companies to develop innovative solutions that will help to address the current issues. The automotive industry is developing cost-efficient methods to utilize waste heat and reduce greenhouse gas emissions.
The number of vehicles on the road is increasing day by day and so is pollution. Thus, it is imperative that efforts are made to reduce emission and waste heat. It is also important to improve vehicle performance so that the user can achieve ROI. One of the alternative approaches to enhancing energy efficiency is to capture and reuse the waste heat lost during vehicle operation. About 20–50% of the energy consumed is lost as waste heat. Other factors contributing to the loss of waste heat include heat convection, conduction, and radiation from hot equipment surfaces and heated product streams. Regenerator, recuperator, economizer, waste heat boiler, thermoelectric generator and other can be employed to extract the waste heat. Economizer is getting traction from multiple industries.
There are both challenges and opportunities with respect to waste heat recovery from existing systems.
Temperature Restrictions and Material Constraints: Materials for thermal waste heat recovery that can retain their mechanical and chemical properties at high temperatures are costly. Thus, to reduce temperatures, waste heat is often diluted with outside air. This further reduces the quality of energy available for recovery.
Application Specific Constraints: The design of thermoelectric equipment is process-specific. For instance, equipment design for the engine and tailpipe will be different. Processor quality control systems can be complicated and compromised because of the heat recovery system.
Extending the Economic Operating Range of Technologies: Although different types of technologies are developed for waste heat recovery, they are not always economical for certain applications, such as dirty exhaust streams. Moreover, the recovery systems installed must be able to overcome the constraints that impede efficient waste heat recovery.
Cost: High equipment costs of waste heat recovery systems make them suitable only for large-scale systems and pose challenges for small-scale operations. High maintenance costs and loss of productivity can result from fouling, scaling, and corrosion of heat exchange materials. Total material costs per unit of energy recovered increase as large surface areas are required for heat recovery systems with higher efficiency and lower temperatures. There is a need for low maintenance, long lasting waste heat recovery solutions that further provide energy for a lifetime and reduce fuel consumption, operating costs, and CO2 emissions.
In a temperature gradient, when electrons flow from hot to cold, thermoelectric materials generate electricity. A thermoelectric material must have a low thermal conductivity, so that one side becomes hot and the other remains cold, in order to generate a high voltage. Traditionally, only expensive semiconductor materials employing rare earth elements such as bismuth telluride, lead telluride, and silicon germanium provided low thermal conductivity along with a high power factor. There is a need for a solution that employs low-cost, high-efficiency thermoelectric materials.
In the waste heat recovery industry, various participants employ common sources of materials such as tellurides, skutterudites, and half heuslers. The industry has also started to employ tetrahedrites and magnesium silicide that are easily available and easy to integrate into thermoelectric power modules and power generation systems. The low-maintenance thermoelectric solution should be able to dispense with the need for compressor fluid and should be highly efficient with respect to continuous power generation over an extended period of time.
Chemical energy to mechanical energy is not converted efficiently in internal combustion engines. So the amount of wasted energy is dissipated as heat in the coolant and exhaust. Researchers have identified two technologies, heat pipes and thermoelectric generator (TEG), which can be employed to extract waste. If these two technologies converge, it has the potential to produce a highly efficient waste heat recovery system.
The CO2 emissions of a car are proportional to its fuel consumption. Car companies are trying to reduce their fuel consumption and meet the target by increasing engine efficiency or migrating to an electric vehicle. The companies have already taken a huge jump to electric vehicles leaving behind the first option. However, it is not impossible to attain the first option. The waste heat recovery system has the potential to increase engine efficiency by converting the waste heat into electricity. This will further reduce the load on the alternator, resulting in a reduction in fuel consumption and an increase in energy efficiency.
But we believe that either the industry has limited interest in pursuing thermoelectric energy harvesting or it has failed to develop a successful prototype. For instance, BMW, one of the key players in the automotive sector, has pursued the technology for 20 years but has failed to bring any viable solution. Other companies such as Renault, Ford, and Honda have also shown their keen interest in exhaust recovery but have failed to bring anything to the market. General Motors is employing shape memory alloy to extract the waste heat. Shape memory alloy is used to convert the waste heat with low grade into mechanical energy. The shape memory alloy identifies the temperature as low as 10 degree C. The other technology which is gaining traction is Organic Rankine Cycle (ORC). Organic Rankine Cycle help to convert the heat with low grade into mechanical or electrical power. Organic Rankine Cycle, is the heat driven technology and currently more promising in the market. Integrating the Organic Rankine Cycle will improve the energy efficiency of the system and will also contribute towards reduction in emission. The companies are also focusing towards lowering the consumption of fuel in vehicle. Companies are putting significant amount of focus on particulate filters to achieve the reduction in consumption of fuel. The original concept of particulate filter was based on heat exchanger geometry of shell and tube. The tube once enlarged comprised of particulate filters. The particulate filter will allow the recovery from the engine exhaust. This will further allow to capture the energy from particulate matter regeneration event. The particulate matter filter will increase the engine efficiency by approximately 15%. In addition, key stakeholders and market research companies have promised 2018 as the commercialization year but none has displayed anything in the market.
Some of the key industries that this technology has the potential to significantly impact are oil and gas, manufacturing, transportation, defense, and mining. Thermoelectric power modules not only improve the capabilities of the target industries in recovering waste heat but are also cost-effective when compared to competing solutions currently available in the market. The solutions can be deployed in a wide variety of exhaust energy sources or temperatures, are highly efficient, reliable for long-term operations, and can be easily assembled and incorporated into the exhaust pipes. The existing key players or start-ups in the waste heat recovery solutions market should also enter the automotive industry. But for any new technology, instilling confidence among partners and investors can be initially challenging. The versatility of new technology might also hinder product development processes by making it difficult to decide on which product to develop.
The companies need to overcome this challenge by collaborating with partners that share their vision. The partnerships will enable them to create working samples using novel technologies at an affordable cost. This, in turn, will help the companies to garner the confidence of investors. In addition, there is an ardent need to put together a global team of experts from various fields to collaborate on many different features of the core technology and ensure a constructive feedback loop.
The technology companies that have a successful operational model for some other exhaust systems in the different industries should try to expand their current market scope and enter the automotive market with huge partnerships or collaborations for knowledge transfer to develop thermoelectric waste heat recovery systems for the automotive industry. There are huge opportunities in the automotive industry — it’s a jackpot.