Controlling the flow — of cash

The Tennessee Valley Authority (TVA) is already the largest electricity producer in the US, but any utility will tell you that size is not enough: profit depends on efficiency. TVA is solving this problem at 12 of its hydroelectric plants using a new condition monitoring system that is increasing operating efficiency by 2-4%. The system, known as Waterview, works by providing the operator with information, minute-by-minute, not only about the operating status of the plant, but also about its economic status.

Waterview has a double genesis. In the mid 1990s TVA was researching a system that would model the performance of its plants and provide feedback on their performance. Simultaneously, US-based Voith Hydro was examining a similar process in its turbine assessments. As the two lines of investigation converged, the benefits of combining the two programmes became obvious, and the two companies decided to collaborate.

The collaboration was formalised two years ago with the formation of Hydro Resource Solutions, the company that would develop and market Waterview.

‘Why develop similar products?’ asks Dick Jones of HR Solutions. ‘Instead we brought together the strengths of the utility and the manufacturer.’ The partners were immediately convinced of the value of the project and the company was fully incorporated from the start. Bringing Waterview to market took more than a year, but the choice was quickly vindicated when TVA decided to install Waterview — chosen despite competition from other systems. But what exactly does Waterview offer to the user? ‘The logic of the system is unique,’ explains Jones. ‘We try to give the operator knowledge of the choices available — and the cost in dollars of making that choice.’ ‘We don’t believe most operators have the data available to weigh the cost of choosing one action against another. Many products can optimise the instant of operating, but they also need data, for example, about the option of saving water for tomorrow. With the costs incorporated the operator has this information available.’

Set up and use

Waterview uses one or more PCs, running on a Windows 95 or Windows NT local area network. The system presents information to the operator in a variety of ways: •The main efficiency module collects data at 5sec intervals using network-based data acquisition equipment and presents it via a summary screen.

•General operating parameters, overall unit efficiency and cavitation levels are presented in a schematic of the turbine.

•An evaluation screen displays the overall efficiency of each unit compared to recent test or manufacturers data. Efficiency loss and unrealised revenue is displayed, and the operator can compare other operating points to the peak efficiency point. On-line data give the operator feedback on the value of potential operating improvements.

•The trends screen offers dynamic and static trending, allowing the operator to compare past and present operating conditions. Dynamic trending allows simultaneous realtime viewing of up to six channels, while static trending allows the operator to retrieve archived data.

•Performance information is calculated using performance information from tests, and based on user specified conditions such as gate or flow limitations.

•Additional modules incorporate and display information on issues such as trashrack fouling. This information can also be expressed in economic terms and illustrates the value of the system. HR Solutions notes, for example, that for a typical five-unit 175MW main river plant, trashrack losses over 1ft represent an annual loss of US$500,000 (assuming an energy value of US$25/MWh).

•Environmental modules include fish passage, cavitation and environmental performance. Data from these modules allow the operator to maximise performance while meeting environmental objectives.

In order to achieve maximum benefit from the system it must be carefully tailored to the conditions at the plant. Waterview incorporates information on technical, legal and environmental requirements to assess the effect of changing operating parameters — the system cannot offer the operator illegal operating conditions or actions. This information varies from plant to plant as equipment, river conditions, local regulations and legal requirements change — at some TVA units, for example, dissolved oxygen is an issue so the environmental module was particularly important. Including these parameters in the system was relatively straightforward. Waterview’s ‘unique selling point’ — assessing economic performance — required rather more invention. ‘Few companies will provide you with details of the revenue scheme for their generating capacity,’ Jones explains.

Waterview solves this by including a means by which the system automatically reads costs and economic data direct from the files of the owner. ‘That way,’ Jones says, ‘the company can keep their costs to themselves.’ With the system up and running at TVA, HR Solutions believes it is looking forward to a successful 1999, and it expects to announce a new customer shortly. The company is confident that hydro operators can increase operating efficiencies typically by 1% at main river plants and 2-5% for tributary plants. Jones believes that on that basis marketing the system will be simple. It is a matter of using historical data to show potential customers what they would have gained over the past few years — if they had been able to keep a close eye on the cash flow.