Creating Cleaner Power from Waste and Renewable Heat

Ian Kemp is our first PhD candidate, a key member of the STEP Lab, and works closely with the student teams. His doctoral project builds on from his post graduate activities at the Lab on, testing and proving small scale machines that can produce sustainable power.

Ian says, exploiting the temperature differences between hot and cold, my research contributes to the development of small portable engines, i.e., power plants. These run on utilising heat sources like solar to geothermal, and industrial to combustion engine heat. The mechanical power produced can not only be coupled to a generator for clean electricity, but also to run water de-salination plants.

As a means to achieving my goals, I have put my hard work and determination in commissioning a unique, flexible test facility, that aims to improve the cost-effectiveness of heat-to-power systems (Fig 1). I am currently running experimental campaigns to identify, performance map of three different Energy Recovery Expanders (ERE) with three different mechanical architectures, using waste gas and geothermal steam.

Purpose built ERE’s are typically designed and manufactured for fixed pressure ratios and temperatures. The off-design working conditions of commercially available machines can be quite different when compared to that experienced in real applications. Further, differences exist in terms of performance between computer simulations and experimental analysis due, in part, to losses such as those of under-expansion, friction, internal leakage, and heat transfer. The parameters of the ERE also affect other system components such as an electric generator by its speed, a heat exchanger regarding a vapour quality, operating characteristics, and ultimately the reliability of the entire system, its production, and maintenance costs.

Kilowatt scale heat-to-power systems usually utilise volumetric expanders, such as piston, vane etc. instead of, turbines, such as radial, axial etc. due to their lower manufacturing costs, good efficiency at low volumetric flow and lower speeds allowing direct coupling to a synchronised electricity generator. The above highlights that the crucial component is an ERE, it has a major impact on the efficiency of the entire system. In the next part of my research, I want to demonstrate the considerable influence that expander efficiency has over the performance of heat-to-power systems. Shown in Fig 2 is the extent of my ERE experimental scope with performance outcomes expected and to answer techno-economic gains.

Fig 2 Experimental campaigns showing the pathway of research with wet steam in phase change and the expected outcomes.

My research study also extends to analysing the multi-phase expansion. For this I need relationship between vortex flow metering and an orifice plate restriction in small bore piping, attempting to record the density of the vapour. This wet steam measurement, will likely identify the vapour fraction. Attempt will also be made to capture this change in phase with shadowgraphy, capturing the image through a sight glass using high speed photography and image post processing tools. I call this, ‘Finding answers at 50,000 frames a second’. Initial imaging (Fig 3), capturing droplets delivered directly into the vertical sight glass have proved noteworthy, and offered a methodology for future experiments.

Initial ERE and image capture results are encouraging, so watch this space, or better still, come over to the STEP Lab. I’m also actively looking to collaborate, sharing my research, and address mutual expectations with interdisciplinary and industrial partners. I can be contacted at I.Kemp1@uni.brighton.ac.uk.

Also, check out the below recording, during the early stages of the works. This was used to set the scene for the main topics of Waste Heat to Power.

Want to know more about the ‘Waste Heat to Power’ themed PhD research? Contact Ian Kemp