Oct 3, 20215 min read

Save 40% on generator fuel consumption with Solar

Updated: Jan 3, 2022

The cost of running a diesel generator is increasing as the price of fuel rises. But with a Generator PV Hybrid system, generator owners can save up to 40% on their fuel consumption.

Every year, the Indian industry spends 3,000 to 3,800 crore for diesel [at a price of 85 INR per litter] to operate their operations during power outages.

Annually India consumes 9 to 11 billion litres of diesel out of which 4.06% of diesel is consumed by industrial generators.

Indian industrialists can save between 900 and 1500 crores of rupees every year by installing a Generator PV hybrid system.

What is a Generator PV Hybrid system?

A grid-tied solar power plant is meant to produce power from solar panels in synchronisation with grid power. Without gird power, grid-tied solar power plants won’t produce electricity.

Grid-tied solar power plants required a reference power source to produce electricity in synchronisation with the reference power source. Moreover, a generator can also be used as a reference power source to run a grid-tied solar power plant.

But there is a catch in running solar with a generator.

First, you need to protect the generator from the reverse power flow.

Since the grid-tied solar power plants generate power in synchronization with the power source. If the load demand is less than the power generation, reverse power will flow from the solar power plant to the reference power source.

Second, you need to make sure the generator is running at a minimum of 30% load.

If the generated power from a solar power plant, fulfil more than 70% of load demand. This will prompt the generator to run lower than 30% of loading. And the continuous running of a generator at less than 30% of loading affect the performance and increase the maintenance cost.

How to run a Generator with a Solar power plant?

To run a generator with a solar power plant, you need a DG PV controller to control the power generation of the plant as per the load requirement keeping the generator 30% loaded.

ZED Advance is the most powerful DG PV controller to grid-tied solar power plants in synch with a generator.

You will be required a set of current transformers at the coupling point of the generator and load to measure the load on the generator. You will also, required a LAN cable to connect the controller with your grid-tied inverter and local area internet.

DG PV controller will use the measurement from control transformers to control the power generation of the grid-tied solar power plants as per the setpoint.

For a generator PV hybrid system, the setpoint will be equal to 30% of the generator capacity. If there are a number of generators operating in sync then the setpoint will be equal to 30% of the quantum sum of the generator’s rating.

For the successful operation of the generator with a solar power plant, the controller will match the following conditions.

If, Solar power generation > Load demands - 30% of the generator rating.

Then Controller will ramp down the output power of [all] inverters to match the below equation.

PVout = Pload - 30% of the generator rating.

And If, Solar power generation ≤ Load demands - 30% of the generator rating.

Then Controller won’t do any change in output power of any inverter.

Also If, Load demands ≤ 30% of the generator rating.

Then the controller will switch off (via control signals over LAN Cable) [all] solar inverters. And there will be no power generation by any solar Inverter.

And when Load demands increases to > 30% of the generator rating,

The controller will switch ON inverters but keep Solar power generation ≤ Load demands - 30% of the generator rating.

There hasn't been a single failure among the more than 200 ZED Advance controllers that have been installed.

Suitable size of solar power plant for Generator PV hybrid system.

To calculate the suitable size of solar power plant for generator PV hybrid system first, you need to know the average power consumption of the facility.

Once the average power consumption is determined you can calculate the suitable plant size by following the method.

Suitable solar power plant size = (average power consumption-30% of generator rating)/0.7

The other method of estimating suitable solar power plant size is by finding the per hour power consumption of the facility in units.

Let’s say, a facility consumes 45,000 units [kWh] and having a generator of rating 100kW then the per hour consumption of the facility will be equal to 4500/30/24 = 62.5 kWh [considering 30 days of working]

Then the suitable rating of solar power plant size will be equal to 62.5kWh minus

Solar power plant size = (62.5kWh - 30% of generator rating)/0.7

You may be wondering what is 0.7 stand for in the above two equations. The peak power generated from a solar power plant is 80% of its capacity for one or two in a year, hence to get the most of a solar power plant throughout a year we considered 70% as the average peak efficiency of the solar power plant.

Best Solar inverters for Generator PV Hybrid system.

To keep the price of solar inverters low, every available solar inverter in the world is still using Modbus as a communication protocol for their inverter. And the problem with the Modbus interface is that it is not a plug and play type communication system.

Hence Modbus mapping of the inverter is required to check the compatibility of the inverter with the Generator solar controller. On the basis of ease of communication, commissioning of the controller and backup support following inverter are the best solar inverters for a Generator solar hybrid system.

#1 SMA: In terms of tech support and ease of communication with the external control devices, SMA is the most favourable grid-tied solar inverter. It has a wide range of grid-tied solar inverters and is easily available. SMA is the best inverter for the Generator-Solar Hybrid system.

#2 FRONIUS: Fronius is the second-best option for the generator-solar hybrid system. And the reason why it is in the second position is due to the lack of tech support. Many times during the commissioning of a controller, Fronius inverters shows errors and it required tech support to short these issues.

And due to poor tech supports, sometimes it takes days to get the right information from them. Hence increase the commissioning time.

ZED Advance is a 4 in one controller for solar power plants. Click here to know more.

#3 DELTA AND ABB: Both Delta and ABB are on third positioning. Because their tech support is far much poorer than Fronius. Two same model numbers of these makes of inverter sometimes required two different settings to communicate with the controller. And it becomes very confusing for the tech engineer to established network communication with them.

It has been seen that both Delta and ABB make solar inverters take more time in stabilising network communication with an external controller.

#4 SUNGROW AND GROWATT: Both Sungrow and Growatt have slow response times. These inverters take more time to ramp up and ramp down power. And that’s why these solar inverters are not the best option for mid (above 100kW) and large size (above 500kW) generator solar hybrid systems.

The reason why these inverters are at number 4 is that these inverters are easily available and establishing network communication with them is not very time-consuming.

#5 SOLIS AND POLYCAB: Both Solis and Polycab have the same electronics. Hence what is valid for one, will be valid to others too. The response rate of these inverters is low too and they take more time to establish network communication with an external controller.