SO YOU WANT TO GO OFF-GRID?
Living well on a limited amount of electricity, such as that produced by solar panels is not difficult, but it can require changes to lifestyle and thought processes.
People choose to go Off Grid for many reasons. For some the motivation is financial, and for others there are ethical and environmental considerations. For many it’s about making an empowered choice to take responsibility for their own energy needs, and for some in more remote locations it’s the only option available.
The first thing to understand is that you become your own power company. If the system develops a fault & you have no power, then you are responsible to have it repaired. This makes your choices around the Quality of equipment, and the company who supply and service it very important. Equally important is the Installer you choose – this will be a long term relationship for the lifetime of the Off Grid system, so you need to choose the best available.
Begin with following these three basic ideas:
- Shift inappropriate loads to other forms of energy.
- Reduce waste through efficiency, and increase conservation.
- Use energy in proportion to the amount available.
The average Grid connected home in New Zealand uses about 15 to 25 kWh per day (3 to 5 people). A low user household (1 to 3 people) uses 10 to 15 kWh per day, and a high user household (4+ people) uses 25kWhr upwards per day.
A typical Off Grid home in New Zealand will normally aim to halve the electrical energy consumption of the typical Grid tied home. This is achieved through Energy efficient home design, use of efficient appliances & fittings such as LED lights and moving high demand resistive loads such as hot water, cooking, and space heating to other energy sources.
A load analysis, a systematic and methodical listing of everything you expect to power in your home, has always been an essential part of good Off-Grid power system design. If you can conserve power by using a more efficient appliance or fitting, then you should. If you cut your total load in half, your system cost also halves. This can be the hardest step in the whole process, so take your time and be accurate. For each load, the expected power consumption and hours of use are listed. Typically for a well installed quality Off Grid system in New Zealand, the approximate cost will be about $6000 – $7000 per kWh of daily usage. It therefore makes a lot of sense to minimise your daily kWh consumption through good design and wise choices.
There are no one-size-fits-all solutions. Every Off-Grid system is uniquely designed to its site, loads, budget, and the personal wishes of the owners.
All forms of energy are not created equal. Electricity is a specialised, high-quality form that is not suited to all applications. It is great for lights, electronics, and motors, plus a few other specialised uses. By matching the best form of energy to its appropriate use, electricity consumption can be greatly reduced while enhancing comfort and convenience.
Five common uses of electricity in conventional grid connected homes won’t typically show up in an Off Grid home. Each of them consumes too much energy to be appropriate when the supply is limited by typical PV system costs. All four of the following use electricity in ways best served by other forms of energy.
Heating and Cooling
Electricity may be used to run thermostats, pumps, and boiler controls, but in an off-grid system it is not usually turned directly into actual heat. The sun’s heat is best used directly. Build or retrofit your home to hold in as much heat as possible by insulating the structure’s walls, ceilings and/or roof spaces, and under floors. Seal gaps and cracks well. If you’re building a new home, incorporate passive solar strategies by using properly sized North facing double or triple glazing and plenty of thermal mass to hold the heat. Heat recovery ventilation can greatly reduce the amount of heat lost in a home, although this does use a small amount of electricity to power a fan. Wood burning stoves are a popular option for many Off Grid homes for space heating. While a Heat Pump/Air Con unit can match Solar production well for cooling, for heat production they generally use the most electricity when the Solar production is at its lowest, so they are not a great match for Off Grid home heating.
Many Off Grid homes will use Gas Califonts for hot water production. If a wood burner is fitted, then a wetback can produce hot water during the Winter months when Solar production is at its lowest. Sometimes it can be a combination of methods that make the best use of the changing seasons. Solar water heaters are less popular these days but they are still available. If electricity must be used for water heating, then install a modern heat pump type hot water cylinder – these can reduce the amount of electricity used by a factor of 3 – 5, this is called the COP (coefficient of performance).
Plan to use a gas hob and oven, not an electric one. But beware: Many gas ovens use electronic ignition “glow-bars” that can draw up to 500 watts continuously when the oven is on. An outdoor barbeque used for cooking in the summer months is also ideal. Some wood burners are also suitable for cooking during the Winter.
In most parts of the country, an outdoor clothesline or an indoor drying rack/clothes horse can be used year-round. Conventional tumble dryers use a lot of electricity, so are generally avoided for Off Grid living. There are newer condensing heat pump dryers available now that use much less electricity, but they are expensive.
Loads with High Surge Current:
Choose water pumps carefully and try to avoid pumps with a high start-up surge or start up current, as many pumps can draw as much as 8 times their normal power rating on start up. It is preferable to go for a pump with a soft start. This significantly affects the size of the Inverter needed for the system. Also carefully consider the power rating of the pump – do you really need a 2000 Watt pump when a 500 Watt efficient model will do the job? Many plumbers are not used to working on Off Grid homes, so they often default to what they normally do without thinking or realising that their simple mistake could cost the home owner $10,000 – $20,000 extra on the cost of the system.
Some electrical loads that may seem to be minor loads due to their power rating, can become significant if they are running for many hours or even 24 hours per day. Examples are Septic tank circulation pumps and swimming pool pumps. Again, choose the most energy efficient models available and set them up on timers, it can have major cost implications for you.
Efficiency is always the first step in reducing consumption. Energy not consumed is energy that does not need to be produced. Every dollar spent on improving efficiency will greatly reduce the overall Solar system costs
LED bulbs typically use approximately 5% to 15% of the energy of an equivalent incandescent bulb and are now very affordable. Consider task lighting rather than area lighting and focus light where it is needed, rather than lighting an entire room. Use multiple lights in different locations, switched separately. Being Off Grid doesn’t limit you to boring lighting. Plan your lighting to meet building standards and functional needs, with maximum efficiency. Then add decorative lighting wherever you wish—just control it separately and use it with discretion and only when you have the energy reserves to afford it.
A refrigerator is one of the biggest electrical loads in an efficient home and is often the single largest daily user of electricity in an off-grid home. Older conventional refrigerators consume two to five times as much electricity as the most energy-efficient new models. Mainstream brands have become quite efficient in recent years and a few selected brands such as GRAM and ELCOLD are highly efficient. By using Energy Star guidelines and the daily energy consumption, e.g. “this model uses 231kWhr/year”, you will be able to select the most energy efficient model to suit your needs.
If you want a full-size freezer, plan to locate it in an unheated outbuilding or portal, shaded from direct sun and
preferably placed in a relatively cool space. Choose the most efficient modern model available. Chest freezers use less electricity than upright models as they often have much thicker insulation.
Also consider other ways of keeping food: Home bottled or canned preserves and vegetables can be a satisfying means of storing food without a freezer.
Front-loading washing machines use less water than top loaders, but they generally have a heating element that takes cold water only and heats it up to temperature, so they can use a lot of electricity. You could use the cold wash cycle, or hot wash only when there is excess Solar power. The newer Inverter type top load washing machines are generally low energy users and are often connected to both hot and cold taps, and some do not have a heating element.
Energy Efficient Appliances:
For all of your other electrical appliances, make sure that you are using the most energy efficient models available.
A laptop uses less energy than a desktop model, as it’s designed to run on stored battery power. But desktop models with LCD monitors are getting more efficient all the time. An inkjet printer uses less energy than a laser printer. Plug peripherals into plug strips so you can easily turn them off when they’re not in use, and be aware of Phantom Loads. Phantom loads account for about 6% of your entire electricity consumption. Any appliances that include a remote control or have an internal power supply are probably phantom loads: stereos, TVs, DVD players, most computers and printers, phone chargers, and the AC adapters used with many small appliances, plus microwaves, and any appliances with an LCD screen which is lit up. The only way to eliminate a phantom load is to physically or electrically unplug the device from its outlet. These loads can be plugged into a power strip, which is turned off when not in use. When building or renovating, add switches to conveniently control outlets intended for known phantom loads, such as audio/video equipment. Use a battery powered clock rather than a plug in model. In an off-grid system there may also be some small DC loads that operate for 24 hours. Make sure that these can be disconnected from the battery power when not in use.
Hydro power is a game changer for Off Grid systems. Micro hydro turbines are made in New Zealand by Powerspout and can integrate well with quality Off Grid designs. To use hydro, you must have a good natural water flow with a reasonable fall or head over the course of the steam or river. Slow moving rivers produce little power, and good hydro resources are rare. However, it’s likely that if you live in a remote area where there is no Grid, then there is a good chance that there may be a suitable hydro resource. One major difference with hydro is that it runs 24 hours a day, so even if the output is modest, the total daily production can be significant. With hydro, the power must be used to keep the turbine fully loaded and from speeding up – an unloaded turbine can spin up significantly and damage its bearings if left running. It’s common to use power diversion with hydro to use the excess power to heat water for example. If you have an abundant hydro resource, it opens up other possibilities such as electric cooking, water heating etc, and possibly even charging an Electric Car. Even if the water resource is seasonal, it’s possible to combine hydro with solar, as they will each will deliver maximum power during different seasons.
While wind can be an abundant resource, harnessing it is not easy. It can be a very unpredictable resource and finding good quality Wind generators is difficult these days. 10 – 15 years ago, there were many good quality home sized Wind generator manufactures globally. However, around this time Solar panels dropped significantly in price making solar a much more attractive option. Wind generator sales slumped and most of these good quality companies went out of business. Wind generators live in a harsh environment and require regular maintenance. Taking the Wind generator down every 6 months to inspect blades and replace bearings is not very attractive to many customers, as a result this regular maintenance is often missed, and failures are common as a result. Wind generators generally require sophisticated control systems and dump loads to prevent them from over speeding in high winds, these systems can increase the cost significantly. One brand that has overcome these issues and remains very popular is the U.S.A made Primus brand. This range of smaller wind turbines suit yachts and smaller Off grid systems as the output is modest. They have the controller built into the turbine so they can be used to directly charge batteries. Independent Power are the New Zealand agent for Primus, with full service facilities for these models.
It’s best to avoid the many cheap Chinese made turbines. These are usually very low in quality and will generally fail very quickly. They often don’t come with the required controller or dump load – this makes them very difficult to install and they will potentially damage other equipment. Another option to avoid are Vertical axis wind turbines or Vawt’s. They are a scam that do the rounds every few years. No wind expert would ever recommend one of these – they have never been proven to work reliably or to produce any useful power long term. Most people who buy one end up with an expensive garden ornament.
Off-Grid Design & Discretionary Loads
Off-grid home power systems are usually sized to meet the electrical requirements of the Winter months, since Winter loads are typically greatest. Shorter, colder days mean more indoor activities and increased use of lights, and most homes will have added heating loads. Shorter days in Winter also mean less solar energy collected. A well-designed home power system in a sunny climate will typically meet 80% to 90% of the home’s Winter based electrical load, usually with a generator making up the rest. Just adding 10% to 20% more solar power capacity won’t eliminate the need for occasional backup charging from a generator.
Predictions of monthly solar irradiance are based on historical averages, and weather patterns never play by the rules
of system design. Sometimes, weeks of bright winter sun and full batteries will prevail. Other times, occasional long
cloudy periods will mean running a generator to keep batteries charged. Plus, occasional equalising (a controlled
overcharge) of a battery bank is needed for some battery types. A power system will need a substantially oversized array and battery bank to eliminate all generator charging, and most budgets don’t allow this. Typically, the goal is to balance minimal generator charging, which will usually occur in Winter, with a PV system that is sufficient to meet the majority of Winter energy needs. A reliable and accurate Battery Monitor or System Monitor must be part of the system design, and installing an AGS (Automatic Generator Start) is highly recommended to protect your valuable battery bank from deep discharges, thus extending it’s life expectancy. Also, having a generator gives you some resilience and backup in the event of a system failure, however it is important to have a generator changeover switch fitted in case this happens.
A solar power system that is sufficient during most of the Winter will provide an excess of charging power the rest of the year, when days are longer and loads are typically fewer. Herein lies a wonderful paradox of off-grid living: After going to the effort to live within the bounds of the system’s reduced output in winter, you may have more energy available than you can use in other seasons. This is part of the magic of off-grid living: The role of the solar array is to provide energy to fill the batteries. Once the batteries are full, the charge controller turns off the power from the array, as there’s nowhere else for it to go. At this time, any energy not used is energy wasted. But as the investment in the power system has been made already and the sun’s energy is free, it might as well be used. This surplus power can be diverted to heat hot water, or to pump water for stock.
A discretionary load is any device consuming power that can be turned off or left unused when cloudy weather hits and/or the batteries are depleted. This is a normal a valuable aspect of the initial system design process. By identifying certain household loads as discretionary, the size and cost of the power system can be substantially reduced. Common household loads identified as discretionary include toaster ovens, coffee makers, clothes dryers, and phone chargers. When the Off Grid system batteries have a low state of charge, use of these appliances should be avoided. Phantom loads like home audio/video equipment, chargers for cordless tools, and the like may also be considered discretionary. Plugged into a power strip, they can be left on nine months of the year and turned off when not in use during the shorter days of winter. A modern large-screen TV and home theatre system is discretionary if there’s a smaller TV for use during winter. “Discretionary” also means that the appliance may be used during cloudy periods, but this may mean using the generator a bit to supplement solar charging.
For most people, toast is an important part of breakfast, a toaster is a basic tool of daily life, and toast is difficult to make any other way. And while a toaster draws a fair amount of power, its run time is just a few minutes. During most of the year, you know that you can make your toast and do all of the other energy-using activities of daily life with the confidence that your batteries will be full by day’s end, or if that day is cloudy, within a day or two. In Winter though, look out the window in the morning, then check your system or battery monitor to see how full the batteries are. On a typical Winter morning when the batteries are at, say, 85% full, and you expect them to be at 100% by day’s end, enjoy your toast. If it looks bright and sunny outside, and you know the batteries will be fully charged by 3 p.m., you may get out the electric waffle iron, knowing that the half-hour use of the waffle iron will be easily handled by the day’s solar input. But if it has been stormy for the last three days, and your system monitor shows the batteries to be about 60%, and it’s still cloudy, use your gas hob to make pancakes rather than toast.
Off-grid living means not that you go without the energy that you need, but that you live more in tune with the natural rhythms around you. Appreciating that your electricity comes from the sun, let your habits be defined by the daily and seasonal cycles of the sun’s patterns where you live. By paying attention to such natural cycles, you will greatly reduce your dependence on a fossil-fuel backup generator.