Skip to main content

Low-temperature heat valorisation towards electricity production

Final Report Summary - LOVE (Low-temperature heat valorisation towards electricity production)

Executive Summary:
Pressed by increasingly stringent environmental and cost saving requirements, the industry sector is constantly looking for measures to increase energy efficiency. In 2010 an ambitious collaboration between academia and industry was launched in the frame of the EU FP7 project LOVE (LOw temperature heat Valorization towards Electricity production), with the aim to investigate the generation of electricity by recovering waste heat at temperatures below 120°C, focusing on the cement sector as test case.

Thermodynamic cycles, and especially the Organic Rankine Cycle (ORC), make it possible to recover low-temperature waste heat to generate electricity. The development of ORC technology is nowadays considerably advanced and there exist many providers of commercial solutions for heat recovery applications. However, little or no industrial experience exists on heat recovery at temperatures below 250 °C, due to the low thermal efficiency at these temperatures and the high investment cost required. The overall goal of LOVE was to evaluate possibilities and limits for power generation in this challenging low temperature range. In particular, LOVE aimed to demonstrate the technical feasibility for one of the most energy-intensive industrial sectors with several instances of non-recovered low temperature heat sources: the cement sector.

To guarantee the successful execution of the project, a consortium consisting of strategic partners from academia and industry has been created. The consortium combined the strengths of leading players in their fields: global cement producers (Holcim, Cemex), major European utilities (EDF, EnBW), innovative equipment manufacturers (Makatec, Cryostar), and academic institutions with active research efforts in the field (MINES ParisTech/ARMINES, Swiss Federal Institute of Technology/EPFL).

Different waste heat source and technical solutions for their valorization were thoroughly investigated. Two demonstrators were designed, built and tested in two different cement factories. The project proved the technical feasibility of power generation by using low-temperature waste heat in real industrial environments. Advantages and limits of different technologies have been highlighted, as well as their exploitation potential in other sector. Continuing collaboration between industry and academia can help enhance technical development and achieve large scale industrial implementation of waste heat energy recovery systems.

The total budget invested on the project was approximately 5 Million Euro, more than 60% funded by the European Commission.

Project Context and Objectives:
In the EU 27, the industry sector represents nearly one quarter of the final energy consumption and one fifth of the GHG emissions. Industries can reduce these losses by improving equipment efficiency or by installing heat recovery technologies (exchangers, heat pumps) to make use of the waste heat inside the plant or exchange it with surrounding factories or residential communities. In the absence of any such re-use, conversion into electricity becomes an attractive solution, but one which still needs development. The aim of the LOVE project (LOw temperature heat Valorization towards Electricity production) was to drive this development, with investigation on available low-temperature (T<120°C) waste heat sources in industrial operations, and development and demonstration of cost efficient innovative technologies for electricity production.

Overall, the project consisted of four parallel research activities organized in several work packages:

1. Development of a methodology for the identification of waste heat sources in an industrial process and for the optimal integration of thermodynamic cycles (WP1).
2. Definition of key performance indicators (economic, sustainability and technical) for the proposed technologies and the evaluation of their market potential (WP3).
3. Manufacturing of two 100 kWe demonstration units to be installed in two cement factories, one of Holcim and one of Cemex (WP2 and WP4).
4. Research on innovative heat exchangers and thermodynamic cycles (WP1, WP2 and WP5).

WP6 regulated management and dissemination activities.

The LOVE project started in October 2010 and ended in March 2014.

Project Results:
All LOVE project tasks have been completed according to plan. Below a short summary of the work performed and the main results achieved:

• A methodology for optimal integration of thermodynamic cycles, based on pinch analysis and process integration, has been defined and applied to the test cases identified in the cement sector (cement mill and raw mill flue gasses). Food and chemical sectors have been also investigated. For well integrated food processes, the real waste heat potential was found at temperature levels which make the integration of Organic Rankine Cycles (ORCs) economically challenging. In case of the chemical industry, the largest potential was found above the temperature range in the scope of the LOVE project.

• Two 100 kWel ORC demonstrators to be tested in the cement sector (recovery of cement mill and raw mill flue gasses at two different cement plants) have been designed and realized. Two different heat exchange solutions were applied (finned tube heat exchanger and packed column heat exchanger) and characterized at laboratory scale before full scale realization and test in the cement plants. Final assembly of the prototypes has been launched in September 2012 and in February 2013 the two demonstrators have been transported to the cement plants for installation and test under real industrial conditions. Theoretical considerations for a 1MWe upscale ORC system have been also performed.

• All equipment and preparation works required for the integration of the demonstrators on the cement plants have been defined and realized before delivery of the prototypes. The demonstration units have been tested for three months each, proving the technical feasibility of power generation using low-temperature waste heat under real industrial conditions. The severe operating conditions to which the prototypes were exposed (acidic emissions, dust and humidity) helped to highlight advantages and limits of technologies and materials used. The achieved overall system efficiency was low, but in line with theoretical calculations.

• The potential for power generation from low temperature waste heat in different industrial sectors (cement, iron&steel, paper, biogas, dairy&cheese) was analyzed, with a special focus on France, Germany and Poland. In addition, the learning acquired with the two demonstrators allowed performing a detailed techno-economic assessment of ORC systems for low temperature waste heat recovery. With the high efficiency solutions used in the LOVE project, the results indicated payback times higher than those generally accepted by industrial for off-production investments. Safety and environmental hazards of ORC installations were also duly evaluated, including a full life cycle CO2 impact by means of a simplified Life Cycle Assessment study.

• Performance of ORC and NH3 based cycles was compared. Model of NH3 based cycles were realized using data obtained from partners’ experimental facilities. The application of NH3/H2O mixtures as working fluid in binary cycles can lead to a significant increase in the efficiency of power generation from low enthalpy source. Advantages and disadvantages of the different solutions were analyzed, including practical issues that partners still need to overcome in their facilities.

• Different prototypes of polymeric liquid-gas heat exchangers were designed, manufactured and tested under laboratory conditions. Capillary tubes based heat exchangers proved easy production with promising results concerning heat transfer and pressure drop. Designs based on polymeric film showed very good heat transfer performance, but challenging manufacturing.

• Options for heat extraction from solids (cement cooler granular material) were investigated. Heat and mass transfer phenomena were theoretically modeled and simulated in the laboratory. This allowed the identification of possible modifications for the cement cooler design so as to enhance heat recovery and make interesting the integration of thermodynamic cycles for power generation.

Potential Impact:
The LOVE project aimed at developing innovative solutions to generate electricity from low-temperature (< 120°C) waste heat sources identified within various industrial sectors and specifically in the cement industry.

The project resulted in several technological developments:

• an innovative hybrid heat exchange for recovery of waste heat from low temperature humid and acid gasses
• a highly efficient 100 kW radial inflow turbine (proven 85% efficiency)
• the realization of small scale advanced polymeric heat exchangers design

The project allowed adaptation and use of the energy integration methodology for valorization of low temperature heat sources and exploration of several thermodynamic power generation cycles, including NH3 based solutions. The potential to extract waste heat from solid material was also theoretically studied, using the cement cooler as test case.

LOVE permitted a deeper understanding of several technical, environmental and safety aspects related to electricity generation from low temperature waste heat by means of Organic Rankine Cycle (ORC). In addition, it generated a deeper knowledge of waste heat available in the industry sector and subsidies/cost reduction required to make power generation from low temperature waste heat economically interesting.

Generation of electricity from gas sources at temperatures below 120°C in real industrial conditions has been demonstrated and efficiency resulted in the estimated range. Key learning can be derived from this experience:

• The size of the recovery heat exchanger is a critical factor at low temperature, as well as the adaptation to the production process.
• Cost effectiveness can be reached if the high efficient LOVE technologies become standard.
• It is fundamental to optimize each component of the thermodynamic cycle, including auxiliaries, while keeping flexibility versus possible variations of the waste heat source.

All partners, especially the representatives of the cement sectors, will be able to implement the learning achieved by means of LOVE, particularly the practical learning obtained with demonstration activities.

The LOVE project has been presented to both scientific audiences and industry representatives on different scientific and business events. Part of the foreground generated by the project has been already published in scientific journals and publicly presented in the course of the meetings held with a specifically created Industrial Advisory Board. Prior to this event, a patent application for waste heat recovery from raw mill flue gasses was filed with the Austrian Patent Office in order to ensure no prior art was generated.

In addition, a special session on electricity from waste heat has been planned within the 27th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems (ECOS 2014, Turku - Finland, 15th - 19th June 2014). The aim of this special event is to share state-of-the-art technologies and research activities that investigate how to turn waste heat into electricity. The session is directed by the Energy Center of EPFL and the key results of the LOVE project will be also presented.

List of Websites:
The public project website is reachable via the web address: http://love.epfl.ch/

Additional information can be requested via the Energy Center of the Ecole Polytechnique Fédérale de Lausanne (EPFL): http://energycenter.epfl.ch/