off-grid

Missteps, mishaps and mistakes – don’t let it happen to you when you go offgrid. Here, Pure Electric* director and regular EG contributor, Matthew Wright, describes 11 problems to avoid when going offgrid.

 

STAYING CONNECTED


1. The first mistake might be the most obvious and that is incorrectly deciding to go off grid rather than getting a grid connection. If a connection will cost you less than $20,000 and you use an average amount of energy then you should connect to the grid. If you don’t connect to the grid you’re going to need a good quality generator which will cost you around $6,000 and require regular maintenance. Compared with a generator over the long term, a $20,000 grid connection is good value. In the case above, I recommend you get a grid connection, 10 - 13.3kW solar and, if budget allows, a Tesla PW2 battery. This will set you up for zero grid power imports and maximum power exports. In this situation you should be able to get paid between 12 and 22c/kWh for exports, making good money from your system while being healthy for the planet.

 

GENERATOR


2. Not having a generator — you need one. I hate fossil fuels too but you must have a generator because expensive solar-battery equipment is not designed to be run to zero power. You also shouldn’t skimp on a generator because the generator will serve two purposes. A. When everything fails your generator kicks in, giving you one to two weeks to arrange for service and support for repairs. B. When your batteries discharge to a pre-determined reserve level, say 15-40 per cent of charge for lithium, or 40-60 per cent of charge for legacy lead batteries, then you want your generator to kick in. The generator should be auto start, which means that if your batteries discharge to those predetermined levels it will switch on. And remember: it needs to be topped up with fuel every time after it runs.

 

GENERATOR UNUSED


3. Generator not running enough. Yes, we design our systems to not rely on the generator but it does need to be ‘exercised’ every so often and you need to consume your stored fuel before the fuel goes off. You can add additives to prolong the life of fuel to say two years instead of one in the case of petrol (diesel lasts longer — up to ten years).

 

SOLAR TOO SMALL


4. Solar PV system too small. There is a minimum solar system size needed to get you through the worst times for solar, such as prolonged periods under clouds — and in most places that’s in the dead of winter when days are short. For a house you need (at minimum) 10 to 12kW of solar. Many times, we’ve found people using 3kW or 5kW of solar who think using large amounts of petrol or diesel on a regular basis is normal for an off-grid system.

Generator use should be infrequent if you have the right sized solar system, ie a system that is sized for cloudy winter periods.

 

 

BATTERIES CYCLING TOO DEEPLY


5. If you’ve got a quality inverter such as a Selectronic SP Pro and an autostart generator then this should never happen because you set the appropriate threshold for the auto-start generator to kick in. So provided you have fuel and have kept the generator maintained then discharging the battery to a damaging level won’t be a problem.

 

HEAT


6. High temperatures in your battery room. It is best to build your battery room somewhere cool – even better to provide active cooling to keep it at 25°C. Mitsubishi Heavy Avanti Plus 2.0kW AC units are a good cooling option and use 310W to remove 2.0kW of heat or 160 W to pump out 1.0kW. Generally, when it’s hottest there is lots of sun around so devoting power resources to keeping the battery room cool is not a big deal. On the flip side you should also stop your battery room from getting too cold if you’re in a cold climate.

 

 

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MONITORING


7. Not monitoring your equipment. It is best to keep an eye on your power equipment: call it a healthy obsession with monitoring. If your system is running well you should be able to see a consistent trend of solar production, on-site consumption, battery charge and discharge.

 

UPGRADES

8. Not having a plan for upgrades – what do you do if your usage is higher than expected? Generally, the answer would be first add more solar or else add more battery storage. Let’s hope the correct inverter has been chosen from the outset. Because replacing the microgrid inverter (which is the heart of the system) while it is still working is a big fail from a design perspective – and an economics fail for the consumer. Make sure you have an inverter that can handle future expansion.

 

NO MEANS NO

9. Wind turbines and micro hydro: these will only work for 1 per cent of people. Most likely they won’t work for you. So if you’re not in a fantastic site for hydro or wind — and most people aren’t — then when the designer tells you ‘no’, you know it means ‘no’.

 

 

off-grid

 

HEATING OPPORTUNITIES


10. Not taking advantage of your system to supply hot water, space heating and cooking services. I have supplied off-grid clients with hot water via a Sanden hot water heat pump. They are fantastic for a number of reasons. They can be timed to run in the middle of the day when maximum solar power is produced. The tanks can be installed inside and have extra insulation around them to minimise energy demand in winter (winter is the design point in most places). Often we put the heat pump under the house or under cover which keeps it out of frosts, prolonging its life and also increasing performance. A super efficient shower head is also a must and provides an excellent return on investment.


SPACE HEATING AND COOLING


Agas and wood fired heaters are still popular but nowadays chopping tonnes of firewood (fires can consume over two tonnes of wood) for an off-gridder can be a thing of the past. A fireplace can be reduced to being something that is useful for two to four weeks only (in the worst of winter). You can then heat your home for the rest of the time with your Daikin US7 2.5 or 3.5kW, or Mitsubishi Avanti Plus 2.0kW (for small bedrooms). This will save you the back-breaking effort (and cost) of needing tonnes of wood and will cut air pollution around you local area.


INDUCTION COOKING


Yes, induction cooking can be run from your solar system and save you the safety issues and effort of organising explosive LPG bottles which used to be the norm for off-gridders. Although your 5.0kW continuous system may not handle 4 hobs running flat out at once, people rarely (if ever) cook like that. So choose the same kind of induction cooktop you would if you were on-grid and enjoy cooking!

 

RUNNING EVERYTHING AT ONCE


11. Awareness is key that you can’t run everything at once in an off grid home. If you want to do a big cook up with your induction cooktop and your electric oven then that’s it — nothing else substantial can draw power from your system (for an entry level 5.0kW continuous system that is). The exception here is with modern AC coupled systems – while the sun is out they might have twice as much real-time power available meaning you can run just about anything. This is why you must familiarise yourself with your system and its capacity via monitoring.

 

 

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SUMMARY


Have your off-grid system designed correctly with a generator, large expandable solar and an expandable battery bank. Have a generator that has a changeover switch so it can run everything without your solar system present (in case of solar system repairs) and can also support the batteries of your solar system when usage is higher than solar output.
Learn to monitor your system, and become as familiar with it as possible. If you do, it will become second nature knowing how many things you can run at the same time, when something is wrong and when you need to take action. And finally, choose your appliances wisely. If you do you can live with all the services and convenience of someone on the grid but in the off-grid location of your choice.
 

by Matthew Wright