Mini-grids powered by renewable energies will play an important role in extending, enhancing and greening electricity services in remote or yet unserved regions. The frequently used phrase “powered by renewable energies” implies a fully renewable energy system without fossil fuel powered generators. Your initial reaction would probably be: “Yes! Finally I can get rid of my thirsty, noisy and dirty fuel guzzler!” Let’s find out if you really should and register for the content-based free live webinar.
We’ll look at the case for a purely diesel powered mini-grid where PV and storage is gradually added to eventually end up with PV as the single source of power (stand-alone). Adding a nearly standard grid-tied PV system to your mini-grid will achieve solar shares (i.e. diesel fuel savings) of up to ~40%. Up to ~50% are in reach if you also add a power smoothing storage system (“buffer”). By the way, at this point the power rating of your PV system might already exceed your peak load (“PV penetration rate >100%”). Don’t worry, this is a standard scenario; the rate needs to rise even more to reach our ultimate goal. Still, we are not yet able to switch off the diesel generator (not even for a limited time). It seems a paradox, but we first need to add another piece of equipment (battery inverter) that takes over the generator’s responsibility to “form the grid”. Combined with an increased storage size, the battery inverter now lets us switch off the generator during the day. Add more storage and the generator will serve as a backup only, i.e. running occasionally to recharge storage with off-times spanning days or weeks.
Our journey to get rid of the generator, having gradually increased PV size and storage capacity, means we can now cover up to 95% of our energy demand by solar. The PV penetration rate might have reached more than 200% by now. Let’s now go the extra mile and get rid of our generator completely: a bit more PV and storage? If only it were that easy! With no generator we lose our backup option. For PV and storage to take over this responsibility (under any weather condition!) a gradual increase of size is insufficient: it needs to be an exponential leap.
While the unit cost (LCOE) of our stand-alone PV-storage system might still be lower than the generator’s, CAPEX are definitely not. So, should you get rid of your diesel generator? Maybe start looking for alternative fuels first.
Free Live Webinar: You are invited to deepen the topic on an interactive level in the form of a free live webinar prepared by Renewables Academy Online. Register now to discuss the topic with the author and RENAC expert for solar energy and rural electrification, Lars Koerner.
Date & time: 04.09.2018 at 15:00-15:45 CEST (find your local time)
This article was written as a guest post by Lars Koerner, Project Director Solar Energy and Rural Electrification, Renewables Academy (RENAC).