Here’s an interesting bit of advice I got from a friend In Dar es Salaam where the power is off 100 days a year …I lived there and we often had 6 weeks without power! So count your blessings such as they are! (excuse the spelling his a Dutchman, a genuine one)
But further to the comments above, Small Holding electriification is all about cost at the end of the day. Dependant on ones location, surpiringly it could well be possible to use Wind as your primary “renewable resource” .
By way of indication, we have put our house onto a battery / solar system providing 9 kW (18kW peak) with abt 22kWh capacity for about the same price as an 18 KVA genset. This has allowed us to downscale to a 12 KVA genset which runs a maximum of 4 hrs daily during 24 hr power cuts which can be up to about 100 days a year. The entire household including bedroom ac is on clean power so fried fridges, computers and equipment are now a thing of the past.
The “Balance of Plant” for Solar PV, Wind or micro Hydro is effectively the same - Charge controller / Battery charger link, Storage Batteries and Inverters to Loads. To be honest, given Eskom’s current “efficiencies” and power quality in any event I would be looking to protect the loads behind an “AVR wall”. This can be accomplished using Load balancing and / or a network of Inverters to provide clean power.
I note that you are presently a 32kW load moving to 50 kW.
In any movement to RE / Utility independance one would need to do a root and branch review of what your loads are and what / when power is required.
The biggest paybacks come in the form of efficiencies and reducing / removing loads. Thus things such as water heating to solar collectors, managing heating and cooling loads by making buildings more efficent and looking into using alternate cooling - evaporative cooling, ground water cooling loops / heat pumps solar collectors for night time warming and just general power management.
THe nest step is to review how one manages major loads - heavy machinery / packing plants etc. These loads may cost effectively require a “heavy” power source and then generators are the way to go, but one then looks to manage “time of day” use so that the major loads and battery charging maximise generator use so that one is not running “spinning reserve”. To this end an appropriately szed Battery bank and Inverter system provides the potential for “peak load” shaving which reduces the generator sizing requirements - one is not running a 30 kW genset for a 12 - 15 kW load with a worst case start load of 25 kW - one runs an 18 kW genset at 80% (better utilisation) and the system provides the starting inrush.
When loads reduce the battery / inverter system provides “base load” power.
Subject to capital costs, availability of existing resources may even allow that one could manage the upgrade from 30 kW to 50 kW with the installation of the battery / Inverter system to handle the increased start loads. Alternately one might look at using a “cascade” genset sytem - a heavy genset for major peak operating loads, a smaller “donkey” for medium load periods or a pair of smaller gensets splitting the load of the main set and alowing single set running during reduced load. The Battery / Inverter system being the key providing load shaving / sharing and carrying base / night / non production period loads.
Then one looks to renewables. These effectively replace charging requirements for the battery system and thus reduce the genset requirements. The quantity of RE is basically a function of cost.
Solar PV curerntly costs of the order of USD 4 - 6 per watt. This is limited to peak Sun hours and effectively provides for 4-6 hours of effective charge so in basic terms - Installed watts X 6 X (system efficiency - 80 - 90% battery inverter throughput) = Solar Pv charge capacity.
Solar lends itself well to low power remote applications such as water pumping, security lighting and fense electrification. Larger systems can be very effectively supplied by solar PV - but always subject to understanding and designing around the system limitations.
Wind can be a viable alternative. Typically presently USD 1 / watt as best I can gather, but with huge variations and effectively I suspect one gets what one pays for. There are some very good modern advanced European units available.
The issue with wind is that efficienies are low at low wind speeds. Power being a function (2.7 to 3) of windspeed - Typically effective power generation requires 18 to 20 knots ( 7 - 10 m/s) with real production at above 20 knots - 10 to 15 m/s upwards. (cut in windspeeds of the order of 2.7 to 3 m/s abt 6 knots are acheivable but with low efficiencies). Effective wind generation also requires large swept areas - a similar relationship between Power and swept area applying.
That said the otput of wind is effectively a function of wind hours. For a Natal location based on averages and empiric guesstimate I would think one would be looking at effective sustained wind speeds of the order of 3 - 5 m/s so say 30 to 40 % of a systems “installed” or “nameplate” capacity which typically at 18 to 20 knots.
Even so significant power can be harvested and some quite cost effective systems are available and can even be homebuilt. Whillst low wind speeds might mean that one cannot acheive high outputs from the turbine sets cost allows for a mulitplicity of smaller sets or installation of a large ( 10 kW upt to 100 kW to MW rated capacity dependant on budget). The power is harvested to the Battery/Inverter system and useable power is a function of effective capacity X wind hours which typically say 18 hours daily.
Having read back specifically into RSA story I would make the following observations :
There appear to be a lot of vested interests and to be honest whillst some very advanced engineering capacity is evident I suspect that a lot of “axes” are being ground. RE seems to be treated as rocket science and, in the same way as water treatment / desalination a significant premium is attached to what is admittedly clever engineering utilising basic fundamentals.
I have seen some formal reports that arive at strange conclusions that doe not detail their reasoning, and one can only surmise that the “unsustainablity” of the installations reviewed derives from either the sytem design or desired use not taking into account the fundamentals limitations, perverted cost allocations or undocumented maintainence / sustainability issues. I also note some large scale wind tests being conducted at sights not exactly renowned for being optimal wind areas.