- Can solar panels provide both my electricity and my heating energy?
Can the PV Solar panels provide enough electricity to also use for electric heating so that I don't have to pay a utility for heating fuel.
In most cases the answer is that it is not economically practical. The exception is for a well insulated house that uses geothermal heating. In that case, it can be practical. For a new home that can be highly energy efficient, this is readily achievable. For a retrofit of an older home, a study of the specific situation is required to determine if this is practical.
Usually when the answer is no, the recommended heating fuel is propane. Wood is fine, but it does not permit you to go on holidays for a few weeks in the middle of winter.
- How much electricity will I need?
- The average not electrically heated household in Ontario uses 20 to 25 kWh per day.
- A typical off-grid year round solar home usually has a solar installation that is about 20% of a similar home connected to the grid and with the same number of people.
- You should not expect to have an electric oven and stovetop in your kitchen, and no electric clothes dryer. (These are normally provided by propane appliances)
- There is no typical case, we recommend a specific energy need analysis to avoid and under or over sized installation.
It is for a year round home. The lead acid battery requires prompt recharging after it is fully discharged to preserve its long life. If a battery is discharged to the maximum depth of charge, and left uncharged, it degrades. This is by a process called sulphation, which shortens its life. Without an automatic generator, this prompt recharge is not guaranteed. You can't wait in the dark for the next sunny day, even though you don't mind some occasional candle light living. If you are away for holidays the batteries require immediate recharging. They can't wait for you to start a manual start generator. A few cycles of discharge without prompt recharging will cause the batteries to last for a year or less. A normal battery lifetime is 10 years. This is as a huge economic impact on the operating cost of the system.
The only exception to this answer is when you have a connection to the hydro grid that you use only for backup.
For a 3 season cottage that used only on the weekends can be different. The PV controller could have an accessory to sound an alarm when the battery requires a charge. This wakes you up to go outside and pull the cord to start the generator. This will permit the use of a far less costly light duty portable gasoline powered generator. A buzzer sounds again to inform you to turn the generator off. This requires that you switch off all loads when you leave, so the battery can't run down if there is no sun for many days. This precludes an electric fridge.
Houses wired to the grid have split phase 240VAC. I recommend doing the same. Wall receptacles provide 120VAC usually from one circuit breaker. Large appliances such as a dryer and stove use 240VAC and have a double circuit breaker. The receptacles are evenly distributed between the two phases. Kitchen outlets are wired differently, with a split 120VAC with one receptacle wired to each of the two split phases. In an off-grid house there are few 240VAC loads, and in many cases none at all.
Reasons for choosing 120VAC
- lower cost, due to one inverter, not two.
- If an inverter fails, you are back to candles and flashlights.
- This can deliver about twice the power to your loads from the same battery.
- The house is wired exactly the same as if it were connected to the grid, improving resale value.
- You could use a 240VAC well pump, if you have a long run to the well, and a very deep well.
- No issues with kitchen split receptacles.
I recommend a system with two inverters. This can be two 120VAC stacked to provide 240VAC, or two 120/240VAC inverters running in parallel. With one inverter, an inverter failure leaves you in the dark. When you have two, you can remove one and send it out for repair and still have some AC. You are not left in the dark.
Cold weather starting is a major concern, and heaters that help the generator start are a necessary evil. The energy that keeps the generator carburetor and battery warm in very cold weather is a constant drain on the house's battery. The size of the battery and number of solar panels must take this into consideration.
Many smaller appliances are fine. We use only true sine wave inverters so all appliances can function properly. However there are many appliances that should not be used, due to the large load, or other characteristics. The list of items that you should not bring is shorter, and will be listed instead of a positive list.
- Electric clothes dryer
- Electric kitchen range and oven
- Older refrigerator or freezer
- Portable electric heaters
- Electric kettle
- Electric frying pan
- Incandescent lighting fixtures (ones that can't accept CFL or LED bulbs)
Cold weather starting is not the only reason. The sound from the generator would also be a problem. There are large commercial installations that are indoors, look up the term co-generation to find out more about this idea.
There are options when your off grid location is not in range of a cell phone tower, or a land line telephone connection for dial-up. THese include terrestrial wireless, where this is available. The most expensive, but available almost anywhere is satellite based service. Xplornet is a Canadian service, and there are a few based in the USA.
A common assumption is that if I have an Internet connection I can use it with Skype or other VOIP service to make telephone calls. Internet service from a geosynchronous satellite has is a long delay for the radio signal to pass a round trip distance of 72,000 miles up to the satellite and back to earth. This translates into a lot of delay. (0.39 second absolute minimum) This delay makes any VOIP unreliable due to the huge amount of echo. Users are reporting a range of 0.6 to 0.8 second delay.
The first approach is to try to use cell phone technology. If you have a very weak signal, or there is a place on your property where you can get a cell phone signal, then there are methods to make this work.
If you are line of sight to a location that has a land line. Consider a point to point radio link radio link with directional antennas to bridge the distance and make access to the wired telephone network possible.
The most important reason is the fuel is stable and reliable down to -42C. Diesel will gel at low temperatures. It does not degrade with time unlike both gasoline and diesel fuels. Usually propane is less expensive than gasoline, and can be safely stored in big tanks so one delivery can last for a year. Diesel engines are hard to start when cold. During the Canadian winter reliable unattended cold weather starting is very important.
Propane also burns cleaner and so a propane burning engine will last longer than one burning gasoline. It also does not have problems running with a light load, which is a concern for diesel generators. A diesel generator with similar capabilities is at least twice the price of propane.
The same fuel is also useful for cooking, hot water heating and for heating.
You wish to have no hydro bill and are willing to invest in a system that over a number of years would cost you less to produce than buying the same amount from the grid. Once you reach the break even point, you have almost free electricity. The almost is due to the finite lifetime of the batteries, which have to be replaced periodically.
This helps to reduce our energy footprint, since all the power produced by the solar installation is green energy. No greenhouse gasses produced.
Other people that have a cottage or year round home and are too far away from the grid to connect. They would prefer to move away from living with a lifestyle that runs a generator any time that you need power, flashlights and propane lanterns. This might be fun for a camping trip, but not as much for a permanent lifestyle.
The heart of this subject is that solar panels are highly dependent on having the entire panel exposed to sunlight. If only one cell in a panel is shaded, the power output can drop to a 1/2 or by a 1/3. In a bulk inverter configuration a portion of the neighbouring panels that are wired in series also suffer. If there is some regular source of shade, then the wiring arrangement of the panels tries to minimize the impact of the shade. The system may provide a higher nominal output by adding more panels as compensation. This is a complex subject, and is one of the reasons that you need knowledgeable people to assess the shade during the site assessment. Unlike with microFIT, distributed inverters are not used in off-grid systems to mitigate shading. A grid tie micro inverter can't be used for off-grid.
- Is a building permit required?
- A permit is required for most roof mounted systems. The fine print in the Ontario building code act is that a permit is required if the face of the solar array occupies more then 5m2 of area, which is a little less than a 1kWh system. So in practical terms, since such a system is too small to be attractive, then nearly all roof top mounted systems require a permit.
Pole mounted and ground mounted systems do not require a building permit, if they do not enclose any space.
- What type of inverters do you recommend?
- Unlike micro-fit and net metering systems, there is no choice between per panel (micro inverters) and string inverters. The concept of a micro inverter does not apply to off-grid systems since the output from the panels is DC, and is used to charge batteries.
String inverters have been in use for a couple of decades and are very mature technology. For off-grid systems these are called "charge controllers." The difference is the output from the solar panels is converted into a DC voltage that charges the batteries. Micro inverters, or per panel charge controllers are not appropriate, and there are none available for off grid use in Canada.
A "charge controller" which is a type of DC to DC inverter. It takes the DC power from the solar panels, transforms it into the correct DC voltage to both charge the battery and supply loads drawing power from the battery. These loads are the inverters converting the battery voltage into 120/240VAC.
- There is a 2nd type of inverter used, there are inverters to convert the DC battery voltage into 120/240 VAC. These are completely different from those used in microFIT system.
- Can You Help Me Install my Own System?
- Yes we can provide advice and on-site supporting consulting services, but some limits apply:
- You must do the electrical wiring yourself, or hire an electrician to do the AC side of the system. This is to wire the house up to and including the main breaker panel exactly if you were going to connect to the grid. We are not in the household wiring business. We will provide some guidelines to the electrician in steps to make the house friendlier to off-grid power.
- We charge a reasonable consulting fee for our time
- We will assess your ability to handle the challenges of such a project, and it should not be the first DIY project you have done. If you are getting out of your depth we will tactfully recommend that you get help with critical sections of the project, or even get a turnkey installation by a solar contractor.
- A DIY installation not only is less expensive, the DIY owner has a better understanding of the system, and is better prepared to do routine maintenance.
- Which way does my roof have to face?
- You get the maximum amount of power generation when the roof has an exact due south exposure. Please ignore any myths to the contrary. Also for a stationary system in the Ottawa Valley a 45 degree slope is ideal, but a 30 degree slope is 2nd best. The 45 degree slope will shed snow better, and will stay cleaner as rain will run down it more energetically. This is the best choice for an unattended system!
If you do not have a roof facing south, you can have increase the number of panels to compensate. Or you can use ground mounted panels.
- What will a tracking system do for me?
- A typical system with dual axis tracking will produce about 30% more energy. However this costs more, and it has moving parts, so it is less reliable. The additional cost will extend the time to break even. Your panels will still be working fine in 25 years, and will still be good for some more years of use. Will the company that made the tracking mount system still be in business in 25 years to service it if it breaks down? These are attractive for microFIT since there is a limit to the number of panels that can can used, but for off-grid there is no limit. It is usually better to add more panels, and benefit from the higher reliability of a system with no moving parts. The cost of extra panels can be less than the incremental cost of a tracking solar panel mounting system.
- Are You Qualified?
- There is no formal qualification standard in Ontario. Our principle has taken a training course in Toronto at a not-for-profit environmental centre, currently said to be the best available. This course included training by the ESA on the application of the Electrical Safety Code to Photovoltaic Systems. In addition he is an Electronics Hardware Designer, and thus understands the electrical part of the system thoroughly. He can diagnose and repair problems with a malfunctioning system. He has spent a career designing products, and is superlative at solving design challenges.
He owns a 10 kW microFIT ground mounted system that is connected to the grid. He did all of the work, and the ground mounted racking is his own design.
He also has designed and built with his own hands a super-insulated house and has done renovations on other houses.
He also is an NRCan certified Energy Advisor, trained to assess the energy efficiency of a home, and to promote better use of our energy resources. This provides additional valuable skills to apply to design of off-grid house systems. This includes determining home heating energy requirements, how to make a home more energy efficient. He is knowledgeable on many types of heating systems.
- How long do the panels last?
- Your Photovoltaic panels should still be producing about 84% of the power they produced when they were new after 20 years.
Here is a picture of a solar panel that is located outdoors north of Toronto that was installed in 1982 and is still producing electricity on the day that I took this photo in 2010. Solar cell and solar panel manufacturing has improved since these were made, and are even more reliable.
- Is A Licensed Electrician Required for hooking up the Panels?
- No. The homeowner has always been able to do this. Recently a lobby group tried to make this require a license, but that was defeated. March 31, 2012, the Ontario Labour Relations Board (OLRB) ruled in favour of the solar industry in its dismissal of an appeal by the International Brotherhood of Electrical Workers and the Ontario Ministry of Labour. CanSIA played a key role providing an industry focused submission illustrating, as the OLRB noted, that the matter had a far reaching impact. CanSIA realized from the outset that while the focus was in Ontario, the precedent set could have spread across the country. The appeal sought to remove the ability of non-electricians to perform solar installations. The issue centred on whether an "MC4 Plug In Connector" is considered a 'convenience receptacle' within the Ontario Construction Project regulations. If it had been determined that the MC4 was not a convenience receptacle, the IBEW argued that only certified electricians (or apprentice electricians) should be permitted to connect them. The ruling means that non-electricians are still able to work with these connectors provided they have the proper technical, health, and safety training.
- Can I use my current refrigerator or freezer?
- You can, as long as it is a modern energy star rated unit for high efficiency. However a model that is specifically designed for a solar home would be much better. One designed for solar applications may use 50% less energy. These appliances run all the time, and provide a significant part of the load on the battery. It can be less expensive to reduce the electrical consumption of these appliances by buying a highly efficient model, or use a propane unit. This is preferred instead of increasing the panel and battery capacity to support less efficient versions of these items.
- The current state of the art for 18 cu ft refrigerator/freezers at listed by the EPA's Energy star program for 2014 shows Frigidare models that use 335 kWh per year. That is 0.923 kWh per day. There are top loading Sundazer 8.1 cu ft fridge and 8.1 cu ft freezer that combined use about 1/2 that amount, and operate on 12VDC. There are Sun Frost models 2 door 14.3 cu ft upright models that uses about 0.480 kWh per day. As you will read elsewhere I recommend that you run these from either 48VDC or from 120VAC with a suitable inverter.
- The potential saving by using a solar specific fridge is about a saving of 0.450 kWh a day.
There are propane fueled refrigerators and freezers, quite popular for RV use. A larger propane model may be the best choice.
- Can I use air conditioning?
- You need a very large solar installation to power the large load of air conditioning systems. Therefore this is not part of most off-grid homes. Instead insulation and shading help reduce the summer heat gain.
There are evaporative cooling systems that are more compatible, or a passive geo-thermal method to provide natural cooling.
- What type of propane hot water heater do you recommend?
- There are three main types:
- Standing pilot storage This uses a conventional chimney, and uses no electricity. It operates at about 60% annual efficiency. This is the most common in existing homes and the least expensive unit. It is the best choice with hard or corrosive well water, as it is inexpensive to replace.
- Power vented Also a storage unit, it uses a 120VAC fan and plastic vent pipe, so it vents through a side wall. this avoids the cost of a high temperature chimney. It is about 10% more efficient in its use of propane. This is the most common in new homes, (using natural gas). They use about 0.25kWh / day.
- Tankless Condensing These are also known as wall hung DHW heaters. They avoid the energy losses due to heat leaking through tank insulation, and out the chimney. This is done by heating the water only on demand, without storing any hot water. These are far more expensive, and the benefit is they are about 90% efficient, and use about 1/2 the electricity of a power vented unit. They are problematic if used on hard or corrosive well water. Under these conditions they are higher maintenance, and expensive to replace. They can also cause problems if the water source is very cold, such as drawn from a lake. This can cause a possibility of a unit freezing.
There is also a non-condensing tankless units that operate at 82%, which is not a good choice. They have all the high initial cost, and all the disadvantages of the condensing model.
We recommend considering a tankless unit only when you have proven low mineral content water without any corrosive properties. Otherwise use the most basic type if a metal chimney exists, or can be installed economically, otherwise use a power vented unit.
- Can I use DC appliances?
- In the past, this was recommended for one reason.
The appliance did not encounter any energy losses due to inverter inefficiency, 100% of the current from the battery was deliver to the load.
There majority of the 12V DC powered appliances were:
- 12V incandescent lights
- an occasional fan or portable TV.
- 12V powered refrigerators
- A well pump
I recommend that you use all 120VAC appliances, and lighting.
Lighting technology has changed, and CFL and LED lighting is the way of the future, and there are many more choices for AC lighting than there are for DC. Inverter efficiency has improved. and even with inverter losses, 120VAC LED lighting produces nearly 3 times more light than an incandescent light of equal wattage.
Now great well pumps from Grundfos have a 120VAC slow start that is ideal for solar powered systems, and are much higher capacity than 12V units.
There are still high efficiency 12VDC refrigerators available for off grid use. However I recommend using the 120VAC versions of the same off-grid refrigerators, if available. For really small systems, a DC fridge still is a great choice.
For other types of appliances, AC appliances are getting more energy efficient. There are so many more choices for 120VAC appliances than there are for DC versions. There is little motivation for manufacturers to develop more efficient DC appliances, since they are made in much lower volumes.
Of all the items mentioned above, then only one which could still justify operating from 12VDC is for refrigeration. This is due to refrigeration being such a significant portion of the overall electrical load. For a 12V battery system, a 12VDC fridge makes sense.
Most sizeable solar installations use a battery voltage greater than 12V. For these systems, drawing some of the load from only part of the battery bank causes problems with an unequal charge in different batteries. This is worth a slight efficiency drop to avoid DC wiring, and the issue of 12V loads on 48V battery plants.
It is more attractive to possible future owners to buy a house wired so that it could be connected to the grid, if a grid connection became available. This is relative to a house with 12V lighting and 12V outlets and 12V deep well pump, which would require some potentially expensive rewiring to prepare it for the grid.
- What kind of Batteries are required?
- Nearly all off grid homes use a type of lead acid batteries. Lithium Ion batteries are too expensive for this application. The three main types used are the traditional flooded lead acid battery, the sealed AGM lead acid battery and the sealed GEL lead acid battery. The first one is the most economical one, and with the longest history of use in this application. They require ventilation and some periodic maintenance, such as adding distilled water when the electrolyte level drops.
The AGM batteries are sealed and are low maintenance, and don't require ventilation. They are more expensive than flooded cells, and don't come in as wide a variety of sizes, and in larger capacities. They excel in low temperatures as they loose less capacity than GEL cells as the temperature drops. They do not work well at high temperatures.
The GEL batteries are sealed and are low maintenance, and don't require ventilation. They are more expensive, and don't come in as wide a variety of sizes, and in larger capacities. They loose capacity faster than AGM as the temperature drops.
- The GEL and AGM sealed batteries are not tolerant of excessive overcharging, and if overcharged they will loose electrolyte through the safety vent, and this can't be replenished.
All these types of batteries should be located in a dedicated area, ventilated if required, and secure from access by children and pets. It should be indoors so the batteries are kept above freezing, as they loose some of their ability in temperatures below freezing. They also should not exceed 100 degrees F in the summer.
- The batteries should be located in a battery box, or on a battery mat as a precaution. In case of a battery leak, sulphuric acid would be released and the extra container provides a 2nd level of protection to your floors.
- Generator start on very cold days?
- Automatic starting backup generators are a mandatory part of most off-grid year round homes. If you wish to go away on holidays, you must have an automatic backup.
Similar to a car, stationary generators are harder to start in cold weather. The amount of the concern depends on your local cold weather extremes. The further north, generally the colder temperatures during the heart of winter. Again, comparing with automobiles, there may be days so cold that your car won't start unless it has been attached to a block heater. The same concept applies to backup generators, some models have "cold weather kits" which warm up items such as the carburetor, battery, and the crankcase. These improve cold weather starting. A significant concern for off-grid applications is the power to keep the generator warm comes from the house's battery.
- This constant load on the battery during cold weather is very wasteful, and requires greater solar capacity. Our recommended approach is to operate the heaters for the generator only for a few hours before the generator is expected to start. This could be done manually by the owner. However we automatically detect when the battery state of charge has dropped 95% toward to the generator start trip point. This results in a 4 day autonomy period to turn on the heaters about 5 hours before the generator start is expected. This is a programmable value. The difference between running these all the time, and in the last 5% of the time before generator start is about two 250W solar panels in the case of an example house with 3.88 kWh average load without any generator heaters at all.
Another way to eliminate the battery warming heater load component completely is by using welding cable extensions to the generator's battery compartment and locate the starting battery indoors. This leaves any other heaters to be managed by the previous methods.
- Generator fuel gasoline - propane - diesel?
- Gasoline fueled generators tend to be portable units, without remote electric start. They are usually used only for weekend use cottages, and less for full time off-grid homes. They are the lowest cost product, and have the shortest lifetime.
- Propane as the most common choice of fuel, and both Kohler and Generac have remote start models. Propane generators last much longer than gasoline powered units and are quieter. They have the least issues with the fuel supply. These are about 2.5 times the price of gasoline powered pull start products.
- Diesel generators remote start ability are about twice the price of the propane models. These have the longest lasting engines, and have the lowest operating cost for fuel. With a block heater these are probably the best for cold weather starting. An example is a PowerLine KS850-T3 Generator Set which uses a Kubuto diesel engine identical to those used on farm machinery. This has a 7 kW rating. The engine can be serviced by any farm equipment mechanic, and has readily available parts. It weighs 50% more than the Kohler propane unit. It probably is the noisiest of the three types of engines. Its lifetime should be much greater than either other type. Diesel fuel does have problems with long term storage. Diesel engines have an issue called "wet stacking" which is a concern when they are operated with a light load, which does not occur with the other types of fuels.
- Will my fuel freeze on extremely cold days?
- If you are far enough north you might experience -42C temperatures, then propane will no longer vaporize (boil). This will have impact on all of your propane appliances, furnace, hot water heater, kitchen range, etc. as well as your generator. Under this particular extreme, a good preventive measure is a heating band to warm up the propane storage tank so some of the liquid will vaporize. It only has to be warmer than -42C, not warmed up to levels that people consider warm. The bigger the tank, the less of a problem you have with insufficient fuel vaporization. If this is unexpected, and -42C is abnormal for your location, there are safe measures to add heat to the propane tank to get the fuel to vaporize. An example is pouring hot water over the tank. Just because the temperature goes down this low, you are not guaranteed that you will need your generator to start at that time. If the temperature warms up during the day, in anticipation you could manually request the generator to start during the warmest part of the day even though the battery is not fully depleted.
- If you had a diesel generator at -42C, you would not be able to cold start an engine either. Winter diesel, known as No.1 fuel (kerosene) has a natural CFPP of -40 °C but it is more expensive than No.2 summer time fuel. Diesel fuel turns waxy and clogs filters, blocking fuel flow. (The Cold Filter Plugging Point (CFPP) is based on a standardized test that indicates the rate at which diesel fuel will flow through a standardized filtration device in a specified length of time when cooled under certain conditions.)
- You might have a problem with the propane tank's regulator in temperatures not quite as cold as -42C, and if you do, you fire up a couple of chemical hand warmers and put them around the regulator, and soon the problem will be solved.
- What use could I do if we have a record breaking low, and the generator won't start? You could have a portable insulated shed that you drop over the generator, and you put a kerosene heater inside it, and let this warm up the generator, and after a couple of hours, you command the generator to try again. Then as soon as it starts, you remove the shed so the generator has enough air for combustion, and for cooling.
- If you go away in the winter for a few week or months, how do I handle this? Turn off all non-essential appliances, and turn the heat down. This should extend the time to run on a full battery to a week or more. Have a friend or neighbour come and check the house about once a week, and have them come on a relatively warm day, and during the warmest part of that day if you are in a cold snap, and have them manually initiate the generator start while they are they to verify that it does start. They may have to manually turn on the generator heaters for a few hours. Once running, turn off the manual generator heater, and the inverter/charger will turn off on its own. This avoids the possibility that the system picks the very coldest time of a cold snap to start the generator when it reaches the point where the battery needs to be recharged.
- Another approach if you have Internet connectivity, and you have a deluxe controller where you can remotely monitor the sate of your solar system, monitor the local weather and request a manual generator start during the warmest time of a cold snap. An extra piece of equipment will be required to allow you to do a remote generator start using the Internet.
- To find the minimum temperature recorded at your location, go to www.climate.weather.gc.ca/climate_normals and locate the nearest weather station to your location. For example Petawawa record low is -41C, and on average has only 6 days a year where the minimum temperature is colder than -30C.