Inverter/Charger Systems
Back in the olden days this system is what you got if you wanted solar. Most applications were for off-grid situations. In spite of the recent proliferation of hybrid systems and deep cycle lithium battery banks the inverter/charger is still going strong, and for good reasons. Key to their longevity is their versatility, easily adaptable to a wide variety of system designs.
All modern inverter/chargers are fully compatible with the various types of lead-acid batteries and consequently are low-voltage inverters. The development of lead-acids has not stood still and these remain the backbone of off-grid installations as well as still being suited to on-grid home installations even with the cost of lithiums coming down significantly. Most modern inverter/chargers are also fully compatible with low voltage lithium packs.
The inverter/charger unit itself consists basically of the DC/AC inverter module, a mains voltage charger and a transfer switch. There are two operating modes; an inverter mode where the household loads are fed from the battery and/or solar energy, and a mains mode where the grid (or standby generator) feeds through to the AC output port via the transfer switch. Whilst in mains mode, if the grid fails then the transfer switch changes mode automatically. Many models have auxiliary contacts for switching back to mains mode if a low-voltage battery limit is reached. There are no MPPT solar charge inputs on the unit and you use one or more discrete component solar charge controller(s) instead. This arrangement offers greater flexibility in the array configuration than does a hybrid's inbuilt MPPT chargers. Likewise the battery management system is not integral and is added externally. There is more wiring involved than with a hybrid but the end result can be very rugged and widely adaptable to meet various installation scenarios.
This system is not the usual go-to option for an on-line household installation but that shouldn't put you off. The inverter/charger can offer greater versatility and is certainly the better choice, if not the only choice, if you'll be using lead-acid batteries. There is a wide selection of inverter/charger power outputs available to cater for various configurations and smaller units are useful for basic energy standby systems or where a household c/breaker board has a critical load section partitioned off. This is how we've arranged our system at home (ref My System).
This makes the perfect system for a sports club or other venue where there is no permanent habitation. The eradication of utility line charges is an immediate permanent saving. A committee member can easily be bought up to speed to take care of its operation. An inverter/charger system is infinitely scaleable to suit a wide range of energy requirements, and once in place can be later upgraded if necessary.
Here is something I would recommend based around a typical energy requirement where social activities are a regular occurance in the evenings and the premises contain full kitchen facilities, freezer and refrigeration and heat pump(s). The final configuration would depend on the outcome of an energy assessment and scaled to match, and of course a smaller system will cost less.
-8Kw inverter/charger with auto generator switching
-15kWh LFP battery pack with BMS
-14 solar panels 440w arranged in either 1 or 2 strings coupled to 1 or 2 solar charge controllers
-6Kw auto-start backup generator
-remote monitor/control unit
Approximate pricing and equipment guide:
- Victron Quattro 48/8000 or Fangpusan XTH8000 with remote unit around $5000. Studer XTH/48/8000 probably $8000-9000.
-2 ea Victron or Fangpusan solar charge controllers $2000, Studer controllers $4000
-14 ea solar panels with associated cables, connecters and roof-mount rails around $8000
-3 ea 5kWh LFP batt packs with BMS around $7500
-6Kw standby generator $3500
-The Fangpusan unit is essentially a Chinese-made version of the Swiss Studer, a top-end unit that has well and truely stood the test of time. From what I can glean the Chinese version is reliable and so represents a fantastic value for money, but not so readily available in New Zealand.
-Victron is a Dutch manufacturer well established in New Zealand and is consequently the best option in terms of ready availabilty with good reliability.
-All three options here are available in a wide range of output ratings and each is fully compatable with any 48volt battery type, and can be matched with a wide choice of solar panel array configurations (ref my article 'solar panels').