Micro-CHP using steam ejector/water turbine (WaterGen)
Lead Research Organisation:
University of Nottingham
Department Name: Division of Infrastructure and Geomatics
Abstract
This project will develop an innovative, generic micro-CHP using steam ejector/water turbine (WaterGen), based on an application of existing steam-ejector/water-turbine/wheel technology, which, can bring additional power generation and
carbon reduction solutions over the next decade by the more efficient utilisation of both natural gas and renewable energy. For safety, stability and cost, water is the ideal working fluid. The new technology will address the fundamental UK energy
supply problems.
The project will include a computer program model the theoretical performance of WaterGen. According to the simulations conducted, for entrainment ratios (W steam / W water) 1/2 to 1/9, efficiency (Wnet / Qboiler) is found in the range of 21% to
34%. For the same operating conditions ORC efficiency is found as ~7%. Additional simulations carried out to determine the cycle efficiency for the increasing steam (motive fluid) pressure entering the injector. Entrainment ratio is kept constant
as 1/5 in this analysis. It is found that increasing steam pressure in the range of 1 -5 bar slightly decreases the cycle efficiency from 31% to 30% whilst for the same conditions ORC efficiency varies between 6.5-7.5%. In overall it is found that injector/water cycle has a promising potential to turn low temperature heat (100-150C waste heat /solar energy) into useful power. For the same operating conditions injector/water cycles can provide 4-5 times higher efficiency in comparison with currently used ORC cycles. Moreover, a "proof of concept" rig will be constructed and operated at UoN based on a steam ejector, designed and supplied by Venturi Jet Pumps Ltd (VJP), mated with a commercially available PowerSpout micro-hydroelectric Pelton wheel/generator specified and supplied by Ashwell Biomass Ltd (ABM). The rig will have a nominal electrical output in the range 1 to 1.5 kW. Turbine water flows will be ~ 5 to 25 L/s with heads of 20 to 100 m. The thermal output will be ~ 10 to 15 kW at temperatures in the range 30 to 70C. This scale is small enough for lab operation,
but large enough to obtain meaningful results and to prove the concept. The latter will be fed into the model to assess the performance of larger installations. The consortium is confident that WaterGen can be scaled up, both by adding more units, commonly done in HE schemes, or by using larger turbine/generator/wheel sets for industrial applications.
The steam/water ejector with low cost and easy to manufacture wheel is expected to have good efficiency in converting steam energy into power. The assertion, sometimes made, that steam ejector pumps have low efficiency appears to be in
comparison with electric pumps; but this ignores the losses in generating the electric power to drive the pump so is not a valid comparison. Reasons for anticipating that the overall WaterGen efficiency will be high enough including the following: 1) the lower vapour pressure of water and its good thermal stability means it can operate at higher input temperatures than organic fluids resulting in higher Carnot efficiency. 2) A recent paper indicates experimental steam/water ejector efficiencies can reach 0.85 of the theoretical maximum. 3) Work by Burns suggests that air injection into steam ejector pump improves efficiency. 4) Although the higher the efficiency the better what really matters in a practical unit is the cost/kWh of the power delivered based on its capital and operating costs...WaterGen is anticipated to be a low cost design and higher efficiency than ORC steam expander. The minimum target for the power output is 10% based on the energy input to the boiler. In a developed system efficiencies of 15-20% could be achievable.
carbon reduction solutions over the next decade by the more efficient utilisation of both natural gas and renewable energy. For safety, stability and cost, water is the ideal working fluid. The new technology will address the fundamental UK energy
supply problems.
The project will include a computer program model the theoretical performance of WaterGen. According to the simulations conducted, for entrainment ratios (W steam / W water) 1/2 to 1/9, efficiency (Wnet / Qboiler) is found in the range of 21% to
34%. For the same operating conditions ORC efficiency is found as ~7%. Additional simulations carried out to determine the cycle efficiency for the increasing steam (motive fluid) pressure entering the injector. Entrainment ratio is kept constant
as 1/5 in this analysis. It is found that increasing steam pressure in the range of 1 -5 bar slightly decreases the cycle efficiency from 31% to 30% whilst for the same conditions ORC efficiency varies between 6.5-7.5%. In overall it is found that injector/water cycle has a promising potential to turn low temperature heat (100-150C waste heat /solar energy) into useful power. For the same operating conditions injector/water cycles can provide 4-5 times higher efficiency in comparison with currently used ORC cycles. Moreover, a "proof of concept" rig will be constructed and operated at UoN based on a steam ejector, designed and supplied by Venturi Jet Pumps Ltd (VJP), mated with a commercially available PowerSpout micro-hydroelectric Pelton wheel/generator specified and supplied by Ashwell Biomass Ltd (ABM). The rig will have a nominal electrical output in the range 1 to 1.5 kW. Turbine water flows will be ~ 5 to 25 L/s with heads of 20 to 100 m. The thermal output will be ~ 10 to 15 kW at temperatures in the range 30 to 70C. This scale is small enough for lab operation,
but large enough to obtain meaningful results and to prove the concept. The latter will be fed into the model to assess the performance of larger installations. The consortium is confident that WaterGen can be scaled up, both by adding more units, commonly done in HE schemes, or by using larger turbine/generator/wheel sets for industrial applications.
The steam/water ejector with low cost and easy to manufacture wheel is expected to have good efficiency in converting steam energy into power. The assertion, sometimes made, that steam ejector pumps have low efficiency appears to be in
comparison with electric pumps; but this ignores the losses in generating the electric power to drive the pump so is not a valid comparison. Reasons for anticipating that the overall WaterGen efficiency will be high enough including the following: 1) the lower vapour pressure of water and its good thermal stability means it can operate at higher input temperatures than organic fluids resulting in higher Carnot efficiency. 2) A recent paper indicates experimental steam/water ejector efficiencies can reach 0.85 of the theoretical maximum. 3) Work by Burns suggests that air injection into steam ejector pump improves efficiency. 4) Although the higher the efficiency the better what really matters in a practical unit is the cost/kWh of the power delivered based on its capital and operating costs...WaterGen is anticipated to be a low cost design and higher efficiency than ORC steam expander. The minimum target for the power output is 10% based on the energy input to the boiler. In a developed system efficiencies of 15-20% could be achievable.
Planned Impact
The impact arising from the project is likely to have significant benefits in the following areas: The UK economy will benefit from the research by increased economy and employment opportunity that may arise from the technology taking up. The market potential for the proposed technology is expected to be substantial as energy savings
and greenhouse gases emissions reduction are set to play an increasing role in the energy sector. This will enable the UK/international companies to develop new businesses. The technology could be internally applied and (or) exported to other countries, such as EU, Asia, Middle East, Africa and China. This may increase UK's economic volume considerably and create new job opportunities, which are expected to be achieved in 5 years commercial development. The significant market potential of the proposed system will provide the UK with economic benefits due to product sales
and employment opportunities. This agreement for exploitation of results will allow the specific technological background of the partners to remain their own property. Only the results of the project will be covered by the agreement and therefore the
agreement will protect the interest of each partner with reference to their technology background.
Being generic, the proposed project has a variety of potential applications for CHP and biomass, waste heat, solar or hybrid sources (e.g., waste heat/natural gas) to power conversion. The early stage funding sought relates to demonstrating "proof of concept" in the lab; consortium experience from previous projects has shown that this credibility is often needed before major industrial companies are willing to become involved in further development. Even at this initial stage an ambitious, but potentially achievable, vision of the business opportunity helps in defining the companies who would be approached to take part in further development, both technical and commercial. The consortium considers that an attractive route to market lies in the manufacturing and operation of self-contained "skid-mounted" sets in the power range 5 to 100 kW.
Although seemingly optimistic, the major components, steam ejector pumps and water turbine/generators, are readily available for this range. In the context of imultaneously reducing carbon emissions and improving the resilience of the Grid, a business model can be developed in which industrial and commercial units are supplied, owned, operated and maintained by companies whose business is providing heating and power utilities as a service, including the interaction with the grid. Essentially such companies become additional providers to the grid with an ability to respond quickly to grid demand through the distributed power networks. This business model facilitates the participation of investment funds, existing power and service companies in addition to equipment manufacturers. Properly constituted would allow the
speedy deployment of a successful generic micro-CHP technology.
The project will benefit the UK in terms of advancing technology, economic opportunities, energy supply security and positive environmental impact, adding value by providing a platform for collaboration between academic and industrial
parties and allowing the UK companies to compete with overseas companies in the field of glasshouses and protected cropping. SMEs will introduce the new technology to the market with the direct creation of new jobs and further employment throughout the supply chain in the energy sector. Manufacturing industries will benefit from the sales of a new product offered both in the UK and overseas.
and greenhouse gases emissions reduction are set to play an increasing role in the energy sector. This will enable the UK/international companies to develop new businesses. The technology could be internally applied and (or) exported to other countries, such as EU, Asia, Middle East, Africa and China. This may increase UK's economic volume considerably and create new job opportunities, which are expected to be achieved in 5 years commercial development. The significant market potential of the proposed system will provide the UK with economic benefits due to product sales
and employment opportunities. This agreement for exploitation of results will allow the specific technological background of the partners to remain their own property. Only the results of the project will be covered by the agreement and therefore the
agreement will protect the interest of each partner with reference to their technology background.
Being generic, the proposed project has a variety of potential applications for CHP and biomass, waste heat, solar or hybrid sources (e.g., waste heat/natural gas) to power conversion. The early stage funding sought relates to demonstrating "proof of concept" in the lab; consortium experience from previous projects has shown that this credibility is often needed before major industrial companies are willing to become involved in further development. Even at this initial stage an ambitious, but potentially achievable, vision of the business opportunity helps in defining the companies who would be approached to take part in further development, both technical and commercial. The consortium considers that an attractive route to market lies in the manufacturing and operation of self-contained "skid-mounted" sets in the power range 5 to 100 kW.
Although seemingly optimistic, the major components, steam ejector pumps and water turbine/generators, are readily available for this range. In the context of imultaneously reducing carbon emissions and improving the resilience of the Grid, a business model can be developed in which industrial and commercial units are supplied, owned, operated and maintained by companies whose business is providing heating and power utilities as a service, including the interaction with the grid. Essentially such companies become additional providers to the grid with an ability to respond quickly to grid demand through the distributed power networks. This business model facilitates the participation of investment funds, existing power and service companies in addition to equipment manufacturers. Properly constituted would allow the
speedy deployment of a successful generic micro-CHP technology.
The project will benefit the UK in terms of advancing technology, economic opportunities, energy supply security and positive environmental impact, adding value by providing a platform for collaboration between academic and industrial
parties and allowing the UK companies to compete with overseas companies in the field of glasshouses and protected cropping. SMEs will introduce the new technology to the market with the direct creation of new jobs and further employment throughout the supply chain in the energy sector. Manufacturing industries will benefit from the sales of a new product offered both in the UK and overseas.
Organisations
People |
ORCID iD |
| Saffa Riffat (Principal Investigator) | |
| Siddig Omer (Co-Investigator) |
| Description | The project set out to investigate whether waste heat derived from biomass or other sources would be sufficient to generate power using a CHP process based on water using a Venturi Jet-pump device. This would be used primarily as a basis to increase the efficiency of existing renewable energy systems, with the longer term aim to be used as a method of supply generation in future periods when power stations are to be closed. On the basis of physical laws governing energy changes between heat to electrical sources it was anticipated the efficiency of the system would not be able to exceed 8-10%, meaning a 100 watt limit to every 1kW of energy input. Albeit this, the innovation of energy provision from a technology with no moving parts was deemed a suitable pursuit for a commercial product development as there were possible applications where this could be exploited. Early on in the first quarter of the project it was discovered through application of modelling processes that the efficiency restrictions placed on the system were much higher than anticipated. Due to additional restrictions in energy transfer imposed due to 'phase-change' processes from steam to fluid flow the system efficiency was compromised to values lower than 1% in ideal conditions. This was on account of the processes mentioned having a geometric impact on the energy that could be physically extracted in the pump transfer process. On construction of the prototype the losses mentioned coupled with system losses rendered the system efficiency lower than 0.1%. Expected system efficiency was very low with the physical energy changes placing limits on what conversions could be made between motive steam and kinetic water flow. It was envisaged that the technology's applications would be in remote or sensitive areas where electrical supply is very difficult to obtain. In these environments, high reliability is certain to be essential, and for this reason specific attention was given to reliable conversion of the low levels of kinetic energy available to electricity. This motivation directed focus on the innovation induction methodology. The squirrel cage induction motor/generator is generally considered the simplest and most reliable electrical machine construction available. Unfortunately, using an induction generator across a relatively wide range of operating speeds required significant investment in control electronics/inverters generating and it is unlikely that this equipment would be suitable in final applications of the overall technology. Being this, the experiment provided opportunity to test the optimisation of the system using Self Excited Induction Generator (SIEG) technology. SIEG provides the necessary AC magnetisation signal required for generation by creating resonant circuits based upon the generator windings in combination with a carefully matched capacitor network. Initial results show that this works effectively and results are included below. The results from testing the squirrel cage device were good and the industrial partner is now pursuing the development of further possible applications it can be used with to optimise DC current output conversion to AC. |
| Exploitation Route | The industrial partner Geo Green Power Ltd took the lead in the project in the building of the prototype rig at their laboratory in Whysall (Nottinghamshire). Comapany technicians and researcher from the University worked together to develop the design of the system and its eventual construction and testing. Albeit currently having a very low efficiency, the prototype demonstrates the concept adequately, and shows how the squirrel cage concept optimises the system output. It is intended that the system is to be used for dissemination purposes at showcase events to promote the concept by the stakeholders mentioned on the aim of finding a suitable partner to upscale the system for application into the remote or sensitive areas where electrical supply is very difficult to obtain. Partners have already begun the process of the dissemination activities mentioned through committing to attending and presenting at an international conference this coming summer 2017, and industry showcase event in the University. A commendation was also received at the Rushlight awards held January 2017. At these events industrial partners were engaged with and it is anticipated a future project will be pursued using EPSRC calls late 2017, early 2018. |
| Sectors | Chemicals Energy Environment Manufacturing including Industrial Biotechology Pharmaceuticals and Medical Biotechnology |
| Description | With the UK goal of decarbonization by 2050 and the electrification of heat for housing stock, incredible stress is being put upon the national grid. mCHP system provide an opportunity to relieve at least part of this stress as well as provide power in location unserved by the national grid. Numerous projects aim to address the need. While many systems show promise, most will be relegated to niche markets due efficiency issues. This project did show promise for a simple system with no moving parts, yet is only applicable to larger, industrial systems due to scaling issues. While the results from this project were unfortunate in achieving the original aim, they highlight the major challenge that is likely set to begin to face society when the energy challenge and security start to face problems in the coming future. In the UK this is centred on the closure of aging power station infrastructure and the lack of appropriate replacement technologies and strategies. The outcomes of this project highlight the issues that are to be faced in pursuit of solutions to provide additional electrical load to increase the efficiency of existing industrial processes. The application aimed in this project was a domestic scale biomass boiler, although with the compromised efficiency levels that were achieved in the experimental results, this was found to be uneconomical. having stated this, the technology does have potential in larger scale applications in remote or sensitive areas where electrical supply is very difficult to obtain. Initial ideas based on this were either deep sea, or highly radioactive areas where human presence is difficult. On the basis of the application having no moving parts and being highly reliable its use would be ideal in these scenarios to generate electricity for low power sensitive electrical devices, reducing the need of both supply to the location and human interaction for possible repair of machinery. For it to be feasible however the applications would need to be large scale, above at least 1MW, and currently the consortium is looking to pursue potential partners in the energy or chemical industries to approach for possible future projects. The challenges faced in this project highlighted issues that can arise in assuming potential outcomes for efficiency in pursuit of research aims related to energy generation. Electricity is difficult to generate using heat without large losses and when there are energy changes, these losses are multiplied. Projects such as this demonstrate the potential faults in assumptions that can be made by both professionals and policy makers and reiterates the requirement for more sustainable forms of generation to meet the growing needs of the UK today and in the future. |
| First Year Of Impact | 2016 |
| Sector | Chemicals,Electronics,Energy,Environment,Manufacturing, including Industrial Biotechology |
| Impact Types | Societal Economic |