Cameron Johnstone

RF-Based Partial Discharge Early Warning System for Air-Insulated Substations

Partial discharges (PDs) generate wideband radio-frequency interference which can be used for noninvasive monitoring of discharges. This paper presents a novel method based on this principle for PD monitoring of substations. The significant advantage of this method lies in the ability to detect PD sources in energized equipment anywhere within a substation compound during normal operating conditions. The results obtained from the prototypes installed in the U.K. and U.S. substations are reported. Results include correlation with apparent charge and daily recordings obtained before, during, and after the failure of a 132-kV current transformer and 69-kV voltage transformer.

A technique for the prediction of the conditions leading to mould growth in buildings

Epidemiological evidence suggests that the presence of mould growth in buildings can have a detrimental effect on the well-being of occupants. Based on an extensive literature review, growth limits for six generic mould categories have been formulated in terms of the minimum combination of temperature and relative humidity for which growth will occur on building materials. These limits were incorporated within the ESP-r system for building energy and environmental simulation in order to provide a design tool which can predict the likelihood and extent of mould infestation. The systems new predictive capability has been tested against monitored data and mycological samples taken from a mould infested house.

Design and testing of a contra-rotating tidal current turbine

Abstract A contra-rotating marine current turbine has a number of attractive features: nearzero reactive torque on the support structure, near-zero swirl in the wake, and high relative inter-rotor rotational speeds. Modified blade element modelling theory has been used to design and predict the characteristics of such a turbine, and a model turbine and test rig have been constructed. Tests in a towing tank demonstrated the feasibility of the concept. Power coefficients were high for such a small model and in excellent agreement with predictions, confirming the accuracy of the computational modelling procedures. High-frequency blade loading data were obtained in the course of the experiments. These show the anticipated dynamic components for a contra-rotating machine. Flow visualization of the wake verified the lack of swirl behind the turbine. A larger machine is presently under construction for sea trials.

Novel, low cost CaCl2 based desiccants for solar crop drying applications

Drying with solar-heated air is satisfactory so long as the sun is shining. To continue this process through the night-time and periods of cloud cover, it is necessary to either store some of this energy in a thermal mass or incorporate desiccants within the drying system. This paper reports the results from studies undertaken to develop three low cost, solar regenerative clay–CaCl2 based solid desiccant materials; establish their moisture sorption and regeneration characteristics; assess their performance when compared with commercial desiccants; and integrate these within a low cost solar drying system for small-scale village-based crop drying. The moisture sorption and desorption performance of the desiccants were characterised in a Fison Environmental Cabinet at conditions of 85% (RH) and 25°C for 120 h for moisture sorption and 50°C and 20% (RH) for 8 h for regeneration. These conditions were representative of the environmental conditions monitored in the solar drying system. The bentonite–CaCl2 (type 1) desiccant gave a maximum moisture sorption of 45% dry weight basis (dwb) while bentonite–CaCl2 (type 2) and kaolinite–CaCl2 (type 3) solid desiccants each gave moisture sorption values of 30% (dwb). It was concluded from the moisture sorption and regeneration characteristics that their application in solar crop drying and air dehumidification is highly useful due to their low regeneration temperatures, sub 100°C.

Developments in solar drying using forced ventilation and solar regenerated desiccant materials

In many countries, grains are naturally sun dried in the field, resulting in large-scale spoilage. Purpose-built solar grain dryers are being introduced with some success, but to be effective, their performance must be carefully controlled to prevent cracking of grains, fungal growth and aflatoxin production during storage. This paper describes some of the performance aspects of an autonomous solar desiccant maize dryer developed for village use in Kenya. Since most commercial desiccants are expensive, a low cost solid desiccant was fabricated from bentonite clay and calcium chloride materials. This desiccant is capable of regeneration at 45°C, has high moisture sorption of 45% (dwb), significantly extends the drying process at night and reduces aflatoxin contamination of the grain. Laboratory and field testing took place to determine the drying performance and allow conclusions to be drawn. This showed the prototype dryer had the capability of drying 90kg of fresh maize from 38% (dwb) to 15% (dwb) within 24 hours.

Photovoltaic-integrated building facades

Photovoltaic (PV) cells, when integrated within a building facade, offer the possibility of generating electric power and heat for local use or export. This paper reports on a project to investigate the practical operational efficiencies that might be delivered from such facades. The results from laboratory experiments and computer simulations are presented: the former were used to develop an empirical relationship between cell temperature and power output; the latter were undertaken to assess operational efficiencies under a range of climate conditions representative of the UK.

Strathclyde university's passive solar, low-energy, residences with transparent insulation

These innovative buildings for 376 students are described from planning to the results of 3 years monitoring. They are to date the Worlds largest demonstration of Transparent Insulation, being a Demonstration Project supported by the European Community and Scottish Enterprise. The factors considered are: design, construction, occupation, comfort, energy characteristics, performance of the Transparent Insulation, including staining by pollution, overall energy consumption, cost effectiveness, practical aspects and important lessons learned. Monitoring shows that commercial energy use is 40% less than the “good” category of official UK indicators and a survey quantifies encouraging user satisfaction generally. The solar fraction of useful gain in winter is 20% of total energy. The south faces of the building have a monthly net gain of energy into the building throughout the year even in mid winter in Glasgow.

Energy, Carbon and Cost Performance of Building Stocks: Upgrade Analysis, Energy Labelling and National Policy Development

Abstract The area of policy formulation for the energy and carbon performance of buildings is coming under increasing focus. A major challenge is to account for the large variation within building stocks relative to factors such as location, climate, age, construction, previous upgrades, appliance usage and type of heating/cooling/lighting system. Existing policy-related tools that rely on simple calculation methods have a limited ability to represent the dynamic interconnectedness of technology options and the impact of possible future changes in climate and occupant behaviour. The use of detailed simulation tools to address these limitations in the context of policy development has hitherto been focused on the modelling of a number of representative designs rather than dealing with the spread inherent in large building stocks. Further, these tools have been research-oriented and largely unsuitable for direct use by policy-makers, practitioners and, ultimately, building owners/occupiers. This chapter summarizes recent initiatives that have applied advanced modelling and simulation in the context of policy formulation for large building stocks. To exemplify the stages of the process, aspects of the ESRU Domestic Energy Model (EDEM) are described. EDEM is a policy support tool built on detailed simulation models aligned with the outcomes of national surveys and future projections for the housing stock. On the basis of pragmatic inputs, the tool is able to determine energy use, carbon emissions and upgrade/running costs for any national building stock or subset. The tool has been used at the behest of the Scottish Building Standards Agency and South Ayrshire Council to determine the impact of housing upgrades, including the deployment of new and renewable energy systems, and to rate the energy/carbon performance of individual dwellings as required by the European Commissions Directive on the Energy Performance of Buildings (EC, 2002).

On the integration of renewable energy systems within the built environment

Future cities are likely to be characterized by a greater level of renewable energy systems deployment. Maximum impact will be achieved when such systems are used to offset local energy demands in contrast to the grid connection of large schemes. This paper elaborates a method whereby passive renewable technologies are deployed locally to reduce energy requirements while active renewable technologies are deployed to meet a significant portion of the residual demand. A modelling system for the identification of suitable schemes is then described and its application to a real case reported.

Development of a Computer Programme for the Prediction and Control of Mould Growth in Buildings Using the ESP-r Modelling System

Based on an analysis of the best published data, critical limits for the growth of six commonly occurring indoor moulds (defined in terms of relative humidity and temperature) have been formulated into a mould prediction computer programme. The fungi were selected as representative of moulds which differ in their relative humidity and temperature requirements to sustain surface growth, and because several were known mycotoxin producing species and of potential health significance. Each growth limit curve was generated from a series of data points on a temperature-relative humidity (RH) plot and fitted using the third-order polynomial equation RH = a3T3 + a2T2 + a1T + ao. The model was incorporated within the Environmental Systems Performance research programme for transient simulation of the energy and environmental performance of buildings, thereby enabling the system to predict the likely occurrence of mould development for fungi which exhibit similar tempera ture/RH requirements to the reference moulds. The model predicts the inter active parameters which give rise to local environmental conditions that encourage mould growth. The systems predictive capability was tested via laboratory experiments and by comparison with monitored data from a moul dy building.