D Henderson BSc, PhD, CEng, MIET.

Chartered Electrical Engineer and Hydro Consultant

Research Interests

Research Projects - Project Summaries - Publications

In 1992 Dr Henderson completed a part-time Ph.D. research study on the subject of a Three Phase Electronic Load Governor for Micro Hydro Generation.

Current and Recent Research Activity at Napier University

Completion of PhD by Naser Odeh as Joint Supervisor on the topic of Optimisation of Solar Air Heating Systems.

Director of Studies and joint supervisor of recently successfully completed PhD candidate Haroon Junaidi on the topic of Optimised Solar Water Heater for Scottish Weather Conditions.

Joint supervisor of PhD candidate Celine Garnier on the topic of Solar Water Heaters.

Joint supervisor of MPhil/PhD candidate Andres Clemente on the topic of Solar energy systems applied for drying woodchip.

Director of Studies and joint supervisor of MPhil/ PhD candidate Yasser Aldali on the topic of the Potential for Solar Generation in Libya.

The work of the Energy & Environmental Engineering Group can be found at their entry in the "Research" link from the School of Engineering & the Built Environment website.

Douglas Henderson - A Three Phase Electronic Load Governor for Micro Hydro Generation.

Micro hydroelectric sets are defined as those with unit ratings of less than 100 kW.  They are often situated in remote communities, particularly in developing countries.  As they are often isolated from grid networks their technical characteristics are such that they require a governor to maintain the frequency at an acceptable level for the users.  The specification for a rural electricity supply is a lot less rigorous, or rigid, as that for Western countries. For a community to afford a micro hydroelectric generating set, the capital cost of the plant must be as low as possible and the plant must be as simple to install, operate and maintain as is possible.

The accepted alternative to the traditional speed governor is the Electronic Load Governor (ELG) which maintains the speed of the set by adjusting an electrical ballast load connected to the generator terminals, maintaining a balance between the total electrical load torque and the hydraulic input torque from the turbine. In this case, the water flow is kept constant and hence the water regulating device can be dispensed with. 

This research project involved the design, development and testing of a microprocessor based ELG for use with three phase synchronous generators. A unit was developed which was later used to control a 15 kW generator in a micro hydro scheme at Ashfield Mill in Scotland.

Haroon Junaidi - Optimised Solar Water Heater for Scottish Weather Conditions.

For the research project, two prototype Integrated Collector Storage Solar Water Heaters (ICSSWH) - one with- and one without fins- were fabricated at Napier University. The collectors were tested in the laboratory on identical experimental schemes to compare their respective performance. Simulations based on analytical modelling were then undertaken and benchmarked using numerous experimental data for validation that was obtained. A high degree of conformance was noted between the two. For a deeper insight, Computational Fluid Dynamics (CFD) analysis was performed. The CFD analysis included both 2D and 3D models that yielded the temperature and velocity profile inside the collector for different time durations. The research also focused on the assessment of the increased heat transfer due to the fins. The difference in the performance with respect to the change in tilt angle was additionally studied.

The remedies to prevent nocturnal losses were briefly touched. In addition to that, for the collector integration with the domestic hot water supply system and plumbing circuits were worked out and the measures for freeze and boil protection were devised.

On the basis of the obtained results from simulations and experiments, the influential design variables were identified. The values for these variables which lead to the optimal design in terms of thermal performance (bearing in mind Scottish weather conditions) were assessed while keeping the overall manufacturing cost of the collector as low as possible.  

Naser Odeh - Optimisation of Solar Air Heating Systems

This solar air system uses the existing roof surface (e.g. south facing slates or tiles) as the solar collector. In summer days, the slate temperatures can be tens of degrees higher than the outdoor air and can heat the incoming air significantly. In this research, a photovoltaic-driven fan is used to draw warm air through roof slates into a duct and deliver it into a house to pre-heat the ventilation outdoor air that is needed in every building. If ventilation air is not preheated, then more auxiliary heating will be required and heating bills will significantly increase. The designed solar air heating system is expected to warm the house, reduce dampness, condensation and health problems and lower heating bills. The main objective of this research is to optimize the design of the photovoltaic-driven fan-duct system through maximizing the total volume of air delivered to the house in a certain period of time.

Celine Garnier - Solar Water Heaters.

This project aims to investigate the behaviour in Scottish climatic conditions of an integral collector storage solar water heater made from aluminium as opposed to stainless steel. A three-month experimental study on the aluminium ICS-SWH was undertaken, confirming the work undertaken by Junaidi et al (2006) on stainless-steel ICS-SWH and determining the performance of the aluminium design. Current work includes field testing of the heater on the roof of Napier University, with and  without typical UK draw-off. To justify the use of the aluminium material, a performance and cost comparison analysis between the stainless steel and aluminium heaters has been carried out, followed by a Life Cycle Assessment (LCA) of the aluminium heater.  A macro model for fluid flow and heat transfer in the ICS-SWH has been developed using VBA and a Computational Fluid Dynamics (CFD) analysis was used to model fluid flow and heat transfer in the 3D SWH geometry.  This made it possible to determine the optimum fin spacing to improve the current SWH shape by modelling a new SWH design. Thereby, a new 5 fins SWH design was suggested and future work will include the modelling of this new design using CFD.

Andres Clemente - Solar energy systems applied for drying woodchip.

The main aims of the present work are, firstly, to outline the drying characteristics of woodchip and, thereafter to evaluate the potential of a novel solar air heating system for this application. Woodchip is a form of biomass fuel, burned to produce energy. It is increasingly becoming an alternative to conventional fossil-fuel sources. The quality of woodchip is strongly dependant on the moisture content (MC) levels. Drying woodchip therefore brings important benefits: increasing the energy density and reducing the weight of the product, making it easier to store and transport. MC in green wood is typically between 60% and 70%. It is generally accepted that MC must be less than 30% before the chip is burned. It is necessary to define the drying kinematics and the effects of key factors such as temperature, humidity and air velocity on the water removal process.

Yasser Aldali - the Potential for Solar Generation in Libya.

The following aims are expected to be achieved throughout this project:

Identify and asses the existing situation in Libya with respect to power generation, transmission and distribution along with the current forecast demand for energy.

Identify the solar energy resource in Libya and evaluate the suitable solar energy technologies to be used in Libya; whether solar PV or solar thermal, and critically appraise the options for electricity generation.

Critically explore the mechanism by which solar generation can be deployed to meet the energy demand, either by bulk transmission to major load centers and/or though rural electrification of regions far away from the existing electric networks.

These aims are in agreement with a national plan has been adopted to raise the share of renewable energy to 10% by the year 2020. 

Papers

Recent publications are listed here. A complete list of publications are given in Dr Henderson's Full CV.

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ELG - Solar - VSD

Electronic Load Governing/Rotating Machine Control

Henderson, D.S. & Pearson, W. December 1997. "An improved control algorithm for an electronic load governor". The Journal of Measurement & Control, Volume 30 pp 293-296. PDF file.

Henderson, D.S., Pearson, W. "Electronic Load Governor - Application of Derivative Control Action for Improving Transient Response". UPEC '98, Napier University, Edinburgh, UK, September 1998. PDF file.

Henderson, D.S. "The Ashfield Mill Electronic Load Governor - Operational Results". Hydropower into the Next Century, Hydropower & Dams, Gmunden, Austria, October 1999. PDF file.

Pearson, W N., Armitage, A F., & Henderson, D S. "A Novel Method For The Performance Modelling Of A Gas Transmission Compressor", Proceedings of ASME Turbo Expo 2002 June 3-6, 2002, Amsterdam, The Netherlands. PDF file.

Solar Energy

Grassie T., Odeh N., Henderson D., Muneer T. Slope Irradiance modelling for Scotland. Eurosun 2004, Germany, June 2004.

Henderson D., Odeh N., Muneer T., Grassie T. Estimating the performance of a PV driven fan in a solar air heating system. Eurosun 2004, Germany, June 2004.

N. Odeh, D. Henderson, T. Grassie, T. Muneer. A new method for estimating the optimum motor constant for PV-driven systems. NorthSun 2005 Conference. June 2005. ISBN 9955-9778-0-9

N. Odeh, T. Grassie, D. Henderson, T. Muneer. Comparative testing of PV-driven roof slate-based solar ventilation air preheating systems. NorthSun 2005 Conference. June 2005. ISBN 9955-9778-0-9

N. Odeh, T. Grassie, D. Henderson, T. Muneer. Modelling of flow rate in a photovoltaic-driven roof slate- based solar ventilation air preheating system. Energy Conversion and Management Journal, Volume 47, Issues 7-8, May 2006, Pages 909-925. PDF file.

Henderson, D; Junaidi, H; Muneer, T; Grassie T; Currie, J. Study of stratification on a integrated collector Storage Solar Water Heater, 9th AIAA/ASME Joint Conference, June 2006. ISBN-13: 978-1-56347-815-4. PDF file.

Grassie T; Junaidi, H; Muneer, T; Currie, J.; Henderson, D. Study of the Modified Built-in Storage (Integrated Collector Storage) Solar Water Heater for Scottish Weather Conditions. EURO SUN 2006, June 2006. ISBN 0 904963 73 1.

Henderson, D; Junaidi, H; Muneer, T; Grassie T; Currie, J. Experimental and CFD investigation of an ICSSWH at various inclinations". Renewable & Sustainable Energy Reviews. Volume 11, Issue 6 , August 2007, Pages 1087-1116 (Online from December 2006). PDF file.

Variable Speed Drives

Henderson, D.S. June 1996. "Variable Speed Electric Drives - characteristics and applications". Energy efficient and environmentally friendly drive systems, IEE Colloquium, London, UK. PDF file.