Hybrid Generation In The Power Generation Hire Market
What Is a Hybrid Generator?
Diesel Generating sets have been used in many different types of emergency, standby, or hire applications for many decades now, and as such, the operating principles are well understood. An engine is connected via a shaft to an electrical alternator; This allows the fuel (usually diesel) used to power the engine, which then turns an alternator to convert the motion of the engine into electricity. These principles have not changed much for over 100 years, although their efficiency has greatly improved.?
Over the last few decades, it’s become clear that the use of fossil fuels, such as petrol, diesel, or natural gas, in general, is problematic in terms of their impact on the environment and the sustainability of their continued use.?Diesel is by no means the worst offender; in cars, for example, diesel tends to emit less CO2 than petrol engines because they use the fuel more efficiently.?
In this period of transition from fossil fuels to other energy sources, it is beholden on us to find ways of improving the efficiency of energy conversion and by virtue of this reduce the environmental impact of what we do. Technologists in the generator industry have turned their attention to this, and the use of hybrid generators, particularly in the “hire” sector, are in ascendancy. When correctly used, these generator/battery combinations use less diesel overall and hence have a reduced impact on the environment.?
In their basic form, a hybrid generator consists of a traditional diesel engine alternator combination which is supplemented by a battery pack. In operation either source can supply the required electrical power.
There are many benefits to choosing to use a hybrid generating set on your hire generator application, which includes:
It is worth noting that these systems can also be used with existing mains supplies, standby generators, as well as renewable energy sources such and solar or wind power.
How It Works
Much like a hybrid car, the battery system utilises power in the most efficient way. Installed between the generator output and the load, the battery system is designed to complement the operation of a generating set, allowing it to operate more efficiently at higher load levels for shorter periods of time or for the load to be fed by the battery alone. There are several ways in which the “hybrid generating set” can be operated, and the savings / environmental impact will vary accordingly.
One such mode of operation would be, for example, as the system load increases or as the battery’s stored energy level is depleted, the battery system will start the generator; the generator will supply the load whilst also recharging the batteries ensuring the diesel engine is running at its most efficient point. The battery system typically seamlessly transfers between battery and engine power, reducing carbon emissions, generator run hours, and therefore any potential maintenance costs.
Another common application is when a generator and battery system combine to power a suite of construction site cabins. Power demand in this type of application is high during weekday days and low overnight and weekends. Typically, overnight the load is lighting, security, and during the winter some background heating. The standard mode of operation would be a generator running during the day and a battery overnight. The generator also picking up battery recharging early in the morning. Whilst this mode of operation is easy to set up and does tick many of the desired performance boxes, such as silent operation overnight, eliminating light load low efficient running of the engine, reduced running hours, and emissions it doesn’t necessarily provide an optimised operation solution. The key is to optimise the performance of both the generator and battery system using them as a fully integrated energy solution optimised for the lowest possible level of emissions.
Optimising the Solution
Always looking to innovate, WB Power Services Ltd was an early adopter of the combined generator and battery solution, particularly on construction sites and 24/7 continuous running applications where low overnight noise levels were key. Early deployments of these packages used battery systems purchased from third-party vendors. WB’s new product integration team initially set about securing an understanding of how the two devices worked together so that they could develop training packages for both the hire sales team and installation, service, and maintenance teams. The early testing work undertaken, combined with a good amount of real-life data, led to the realisation that this combined package had much more to offer than was being sold by third-party organisations. It led to a determination within WB to fully explore and quantify potential savings for clients, to ensure our teams new how this could be achieved and has ultimately led to the development and production of our own NetZPack battery solution.
WB has undertaken extensive development and testing of the NetZPack product ensuring that operation of the generating set and performance of the battery system are fully optimised ensure we are securing the maximum efficiency of operation when running on generator and secure the maximum possible life from the battery system too. We should not forget that there are significant environmental costs associated with the production and manufacture of Li-Ion batteries.
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Testing
WB undertook a wide range of testing to both optimise its third-party battery fleet but more so when developing the NetZPack product. This was important for a wide range of reasons: -
Worked Examples
As part of WB’s research and development programme, it undertook a number of monitored field tests on a range of generator and battery system combinations and various load types. One such evaluation was undertaken when working in conjunction with one of our DNO utility clients, who was undertaking some overhead power line replacement work in an area with just a few residential properties. This sort of application is where a combined generator and battery system work well together.
In this instance, the load assessment provided by the client indicated that whilst there would be a load on the system 24 hours per day, there would likely be three very distinctive peak periods of loading: morning and lunchtime, with the largest and longest coming during the evening. Armed with a more detailed profile, WB selected a Kohler J66 generating set housed in a close-fit canopy and extended-run base tank with a NetZPack 30/75 battery unit.
The red line on the first graph shows the actual load profile during a typical 24-hour weekday period. The green blocked areas show periods when the generator was running. The blue line on the second graph indicates the state of charge of the battery system.
The battery system is used to supply the load during periods of lighter loads. The generator is used to supply the load during periods of higher load while also recharging the battery system. When used in this combination, it can be clearly seen that the generator:
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o?? Avoiding periods of light load running issues
o?? Avoiding inefficient burning of fuel at low load levels
o?? Runs for a shorter period reducing running costs and maintenance requirements
o?? Is typically always running at a heavier load level where the engine is:
o?? Running at optimal engine temperature with minimum
o????l/kWh fuel consumption
o????Lowest level of emissions per kWh
In this particular example, the results were as follows:
Important Takeaways
Maximum optimisation can only be achieved if the vendor closely matches the generating set to the battery system. This isn’t just down to getting the correct set rating; it is down to the performance of the specific engine type or manufacturer, as set and engine performance does vary. WB understands this well and is able to optimise this within the NetZPack operational software.
The key to a successful deployment and use of a hybrid generator package isn’t just about reducing fuel consumption of the generating set, it is also about optimising the performance and the life expectancy/life cycle of the batteries, as there is an environmental impact in the materials used and manufacture of these batteries. WB’s extensive product development testing and operational experience have found that securing optimal performance isn’t straightforward but needs to be based on a wide range of design and operation considerations, such as:
With so many of these variables outside the control of the operator and supplier, all of which will impact the operational performance and life cycle of the product, it can be seen just how important it is for the vendor to provide the right product package for the power requirement and load environment if both operational and life-cycle performance are to be maximised.
The knowledge built up during the expensive development testing and operational testing of the NetZPack product has been locked into NetZPack’s operational software and product training imparted into the Hire Sales team when dealing with client enquiries.
The NetZPack is also able to use power provided from other sources such as renewable energy from wind or solar with either or both working in combination with the generating set. Additionally, the system has an input for a grid-based mains supply making a great source of power where the grid supply is unstable and subject to frequent disruption and hence enhancing the reliability and of the grid.
Author
Business Consultant
WB Power Services Ltd
Geoff Halliday started his career as an apprentice working for Square D (later part of Schneider) before moving into the critical power sector where he has now worked for over 40 years, splitting that time equally between both the UPS and standby diesel generation sectors.
During this period Geoff has held several roles ranging from Customer Service Engineer, Project Manager, Technical Director, Sales Director through to Managing Director.