Growing environmental concerns are increasingly putting limits on the use of diesel generator (DG) sets in cities, while better availability and quality of grid power are also lowering the need for the utilisation of DG sets. Thus, to cope with these challenges, the genset industry has been working towards adapting to new technologies and solutions in order to meet the demands of higher power reliability, reduce emissions, lower costs and remain always “online”.
A look at some of the new and emerging technology options in the genset market…
Adding digital controls
Unlike analog systems, digital control systems are able to provide real-time status of all major components within the system. Parameters such as engine oil and coolant levels and temperatures, battery charge status, fuel levels and the condition of transfer switch in the power distribution system are now accessible on a computer screen on the digital master control in the control room, or even on a secure remote terminal connected via the internet. The availability of such information makes it easier to manage a facility efficiently and economically. Further, digital control systems are able to perform logic functions and can help in reducing exhaust emissions while starting the generator set.
An important application area is the use of digital paralleling solutions. Paralleling gensets is not new and many facilities run several generators in parallel to ensure power reliability and guarantee sufficient emergency or backup power. Paralleling generator systems involves synchronous operation of two or more generator sets connected together on a common bus in order to provide power to common load. Paralleling generators help improve reliability, increase load management flexibility, manage run time on engines and provide maintenance flexibility, reducing generator costs. With a paralleled generator system in place, additional generator capacity or redundancy can be added as needed. Adding digital controls helps to simplify operating several smaller generators in parallel. Sophisticated electronic controllers help minimise the number of controls, providing an inherently more reliable system. They also integrate paralleling switchgear into the system, so that a third-party switchgear solution is not needed.
Gas-based gensets are another emerging technology in areas within easy availability of natural gas. Instead of the typical choice of diesel or liquid fuels, these gensets run on natural gas. These gensets are not only more compact than DG sets but also have lower operating costs and noise levels. They are also environmentally friendly and can go a long way in cutting the economy’s carbon footprint by reducing diesel consumption and expanding the share of clean fuel in the country’s primary energy basket. Natural gas generators burn cleanly with very little waste. Also, these generators have an advantage over their diesel counterparts from a storage standpoint as diesel is only good for around 24 months in storage and storing large amounts can be expensive. Moreover, the lower operating cost of gas gensets as compared to diesel gensets, along with growing construction activities, is further boosting the demand for gas gensets in India.
Another emerging technology trend is hybrid DGs that combine diesel gensets with a renewable energy source such as solar, wind or biomass. With this, the dependence on diesel decreases and helps in complying with the environmental norms. Renewable energy generator hybrid systems can double or triple the amount of continuous service time compared to a stand-alone diesel generator with an equivalent fuel tank size. Large-scale portable batteries can be paired with any kind of mobile generator for the provision of additional reliability and reduction of generator runtime. Storing energy and relying less on generators, batteries can go a long way in the reduction of greenhouse gas emissions and carbon footprint in the power sector.
The most common hybrid technology is diesel gensets, combined with solar photovoltaic (PV) systems. Using two sources of energy makes it cost effective (as diesel is expensive) and also resolves intermittency issues, purely using solar power. Typically, during peak sunlight hours, an automatic digital system controller maximises the load on solar panels and produces energy from PV panels. At the same time, power from the diesel engine provides the required frequency and voltage, which firms up direct current produced by solar panels, stabilising the load. DGs are used to fill the gap between the power generated by the PV system and the load. Moreover, battery storage can be used to enhance the overall system performance, ensuring that the necessary energy demands are met. In addition to this, an energy management system (EMS) can be included to optimise the system due to the fact that diesel gensets’ capacity is limited and solar energy production is inconsistent. There are multiple benefits of solar-diesel hybrid systems. These include increased PV penetration, minimal energy wastage and uninterruptable power, that is, even when the grid fails or PV production is not enough, the system still keeps going. Hybrid systems can also be programmed using an EMS. Diesel gensets with solar hybrid systems mostly include a battery or energy storage. The battery storage also provides stability for the current flow. The initial addition of battery storage to the configuration of a diesel-solar hybrid system involves high capex costs, but there are high operational cost efficiencies in the long run.
While these technologies are promising, there are certain caveats. For instance, the goal of the PV-diesel hybrid system is to reduce the diesel operation hours and 24×7 electricity deliverance for customers. However, before applying this technology, some prerequisites are necessary such as open land enough for locating PV arrays and batteries and availability of well-maintained and automated DGs. One of the major issues is that most of the real conditions on sites are not supported by hybrid technology. For instance, the existing DG is not provided with automatic start/stop control and there is no open space available, close to the DG where PV arrays can be installed. The operating system in the fully automatic mode without automatic start/stop control on the existing diesel is not capable of performing optimally, because the system is bound to shut down when the operator does not turn on the DG. It would be better if the system is operated in semi-automatic/ run source mode, wherein the DG is supposed to be started or stopped by the operator as per their schedule, while synchronisation between the inverter and diesel generator is still in control by the control unit. Another on-site issue that appears is when there is no open space available for PV arrays close to the DG. In that case, PV arrays have to be located far from the DG. In such a condition, it could also be done by run source mode but the load sharing between the inverter and DG will be done by the operator, and there will be no blackouts when the DG takes over the load. The options of manual mode are used when there is a problem in the inverter and the system runs with diesel only, or during peak load and low battery levels.
In summary, because of their established technology and reliability, DGs remain the go-to option, even after the advent of new distributed generation options. However, given the government’s increased focus on emission control, genset manufacturers would need to continue focusing on the development of technologies that offer effective emission control and optimised fuel consumption.