Products - Wind Diesel Systems

1.1 Technical Outline on Wind Diesel Technology (see also the link Sagar Project)

Wind-diesel is the generic term given to energy supply systems that combine diesel powered electrical generators, which provide prime power, and wind turbines, which operate when wind power is available to reduce the load on the diesels and displace diesel fuel. Wind-diesel systems have been utilized for many years, in "low penetration" applications, where the wind plant provides relatively small amounts of power and energy relative to the total system requirements. Systems with higher penetration levels, where the wind plant can provide as much as several times the total plant power capacity, have been successfully tested in a number of countries. At high penetration levels, diesel may be turned off in high wind power conditions to allow the system to operate in autonomous wind mode. During autonomous operation, a dump load is required to maintain the stability of system frequency and synchronous condensers are used to provide voltage regulation. Turning the diesels off during periods of high wind power has a very positive impact on fuel savings but the concept has been slow to find application because of concerns about system reliability and power quality when operating in autonomous wind mode.

To address these concerns, the Wind-Diesel Integrated Control System (WDICS) was developed. This is a high penetration control concept that supervises the operation of the entire power plant integrating the control and dispatch of all electrical generation sources, including diesel plant, wind plant and demand side management options.
WDICS (see attached schematic) is designed to fully integrate the control and operation of wind powered generating plants with diesel generating systems. Incorporating advanced control concepts into wind-diesel systems enables plants to operate with higher reliability and higher efficiency, with reduced operator intervention. WDICS can be used with different levels of integration, with full integration (where the WDICS system fully controls the operation of the plant) and limited integration for retrofit installation where the existing plant operation does not lend itself to full control.

WDICS enables all electrical system generating equipment including diesel plants, wind plants and the dump load to be controlled by a single supervisory control system. It can be integrated into a range of energy alternatives, such as demand side management programs and it provides a platform for the "Total System Energy Management" concept that optimizes the utilization of energy.

1.2 Wind Diesel Technology background

The term Wind Diesel Technology is widely used for a variety of systems. Of interest to the customer are finally two aspects:

A) The penetration level (pt) - the quantitative factor of effective Wind-power to Diesel-power, expressed as the average quotient of the two.
pt = kW(wind)/kW(diesel)

Standard penetration level limits and their application

Due to the operational characteristics of diesel generators, the fuel consumption is not linear to the load. Optimum load / fuel factor is usually achieved at 60-75% of the rated output. At this point a Diesel generator will generate between 3-4 kWh per liter of fuel. Unfortunately it will consume almost 20-25% of this amount of fuel under "no load condition".

In the Wind-Diesel System with "high penetration" the Diesel generator is switched off when wind-power generation is sufficient to cover the demand. The highest fuel savings can therefore only be achieved at "high penetration levels".

"High penetration levels" pose some boundaries:

1) Since the nature of the system requires autonomous operation of the wind turbines, the voltage and frequency has to be controlled.
(Dump load and synchronous condenser)
2) A Fast responding back-up power supply is necessary to prevent power fluctuation/failure in case the wind speed suddenly drops or the load increases unexpectedly. (Slip clutch on Diesel).
3) The necessary control system and interface is costly, usually these systems are restricted to Wind Turbines in larger applications.

Table: different Energy Scenarios and operational modi in "high penetration"

B) The cost:

Initial investment for Wind-Diesel Systems is quite high in comparison to grid connected wind farms. The reasons are that smaller wind turbines come into use and that a sophisticated control system has to be installed. Typically the sites chosen for a system of this kind are remote and difficulty in access and logistics of installation increase the cost.
However the economical analysis shows that a return of investment can usually be achieved during the first 8 to 12 years of operation. Given a life expectancy of 25-30 years the savings are considerable.

1.2.1 Technology available in India

Fully integrated Wind Diesel Technology was first demonstrated in India in 2002 at the Sagar Island Wind Diesel Project. The system was supplied and installed to WBREDA by Auroville Energy Products (AEP) who have their head office in Tamil Nadu. The project was jointly funded by MNES, ICEF and WBREDA.

At present, AEP is the only supplier in India who has successfully demonstrated Wind-Diesel technology in India.
Sagar Island Wind Diesel Project - INDIA (high Penetration)

Whereas many Wind-Diesel Systems with medium to low penetration levels have been executed, the only well proven technology on the market suitable for high penetration levels is provided by AWTS (Canada) / AEP (India)

1.2.2 Control systems

The Wind-Diesel Controller WDICS interfaces with the Wind-Generators via analog and digital communication lines. The Wind turbine controllers have to be equipped with Programmable Logic Controllers (PLC), which allow this method of data transfer. These have to be programmed to allow remote Start/Stop, individual monitoring of wind-speed on the tower, rotor speed and net Power.

1.2.3 Wind generators

Today, Wind Generators of large variety in type and brand are being manufactured in part, or wholly in India. The range is from 50 kW to above 1 MW. Characteristically the price per installed kW capacity decreases with size. Therefore a bigger machine would usually be preferred to a smaller sized machine. However in a Wind Diesel application in a remote site specific requirements have to be considered.

a) The diesel generator capacity to start the wind turbines - Asynchronous wind generators require a "stable grid" for start-up synchronization. Individual diesel -generator capacity has to be in the order of 2-3 times the rated output of each wind generator to enable seamless start up and synchronization.

b) Ability to adjust output-level to power-requirements - As the wind-power generation may at times exceed the load, power management in reasonably small increments should be possible. When the power output exceeds the demand one wind turbine is switched off. This limits the size of the dump load.

c) Limitation of transport and roads in remote locations.

d) Limitation of erecting facilities available in remote locations

Addressing the above points we offer the AEP 15/55 Wind generator with a rated capacity of 55kW in our Wind-Diesel Projects. The machine has been optimized to interface with the WDICS.