1. What is variable speed diesel?

Conventional diesel generators run at a fixed speed, for 50Hz systems this is generally 1500 rotations per minute (rpm).

Variable speed diesel generators can run at any rotational speed, as determined by which speed provides the greatest efficiency for any load setting. Renewable Ready variable speed diesel technologies adopt permanent magnet generators for their high efficiency and power density.

The generator is still able to meet the network frequency, as a power converter is placed between the generator and the load. The role of the power converter is to ensure the variable frequency output of the generator is conditioned to meet the network frequency. This approach is common across wind, solar PV and battery technologies, which generate at either variable speed or are direct current (DC) technologies. Reliance on a power converter does not reduce the reliability of the approach, however it does improve the power quality and security which can be offered to support the network.
The ability of the variable speed generator to select its preferred speed setting is responsible for the dramatic performance improvements. The generator is no longer constrained to a very narrow speed reference (akin to driving your car without ever changing gear).

Efficiency gains at low load are in the order of 40% for variable speed diesel application. The engine also gains an increased maximum power output at increased shaft speed.

2. Why have diesel generators developed as fixed speed, if it is inefficient?

Fixed speed configurations are appropriate for constant, steady load applications. However with the emergence of cheap clean renewable generation, the load seen by the diesel generator is highly variable. Fixed speed diesel generators are poorly suited to renewable pairing for this reason.

3. Doesn’t the power converter introduce losses to the system?

The introduction of a power converter is responsible for a 1-1.5% loss, however, given the ability of a variable speed diesel to run without load limit constraint, the approach returns a 20-30% improvement in renewable penetration, more than compensating for any converter inefficiency.

4. Which diesel engine supplier and models can be used?

We configure our variable speed diesel generators under license in Bangalore, India. Our manufacturing facilities are TUV ISO9001 certified. Any diesel engine model can be specified to align the asset to your existing diesel fleet. The advantage of this approach allows for a consolidated spares holding and maintenance program. Should you not have a supplier preference we recommend Cummins QS and MTU 1600 engines subject to your capacity requirements.

5. What warranty is offered?

Renewable Ready warrants original equipment manufacturer warranty conditions, to the Buyer, under the terms of the Conditions of Sale that the Goods supplied are free of defects in material and workmanship at the time of passage of risk to the Buyer. The limitation period for defect claims is 6,000 hours of duty. In all cases it shall end no later than 36 (thirty six) months after Renewable Ready has given notification that the Goods are ready for dispatch.

All warranty provision are backed by our engine suppliers and system integrator, the later with a group revenue exceeding $15m p.a. and employing over 265 staff across three facilities.

6. How much does it cost?

The additional costs are in the power converter, however the payback period with consideration for the significant fuel savings is typically 6-12 months. Please get in touch for a detailed price inquiry.

7. What does it look like?

Some much like a conventional diesel asset, you won’t notice the difference (except for the massive fuel savings, and less noise, and lower emissions …..)