Solar energy for the average person’s home is becoming more and more accessible. However, technological terminology can sometimes be overwhelming. When we think of solar panels, what we picture is called Solar photovoltaic (PV). It’s specified because there are other major types of solar called Concentrated Solar Power (CSP) and Solar Thermal which generate energy from the sun’s heat. Even basic concepts, such as thermal versus photovoltaic or grid-tied versus off-grid, may be confusing. Yet, the concept of solar energy is quite simple: conversion of energy from the sun into useable energy for the consumer. In this article, we discuss how solar PV systems work, the economic and functional advantages of types of photovoltaic solar energy in business and residential uses and how to design the optimal photovoltaic system.
How does photovoltaic (PV) energy work?
Solar PV systems, although seemingly complex, are very simple. A PV solar panel (module) is comprised of multiple PV cells. Each cell has two layers of a conductor material—often silicon—sandwiched together, one with a negative charge, the other a positive charge. Remember how an atom is made up of protons, electrons, and neutrons? The light energy from the Sun knocks electrons loose from the conductor material in each cell. These loose electrons travel along a bus or conductor bar to create a flow of direct current electricity. The many cells combined form a solar panel sending all these electrons into the current. The number of cells in the array or series determines the power produced by your solar panel. These traveling electrons create DC electricity that an inverter changes to AC, the electric current we use in our homes for power.
What does “off-grid” and “grid-tied” mean?
In both these terms the word grid is used, this is referring to the local shared power source such as the powerline connected to a home. A common misconception of solar systems is thinking that it needs to be the sole power source to the home, essentially going “off-grid.” However, there are actually three primary PV systems: off-grid, grid-tied, and hybrid systems.
The off-grid systems operate independently of the local power grid, relying on batteries to save the energy for use when needed or when the sun is not providing power generation. Most often, they exist in areas where access to grid power lines is limited, or where the homeowner wants to be free of the electrical network. They also are appropriate where there is limited electrical demand, such as for charging recreational equipment batteries, electric fences for livestock, or low-power systems such as landscape or yard lighting. Off-grid systems produce power for your home during the day, but they must also produce excess energy that is then stored in batteries for night and for days with heavy cloud cover. Off-grid systems must be sized to produce the required energy during any season. This results in the system often being sized much larger than a grid-tied system so enough energy is still produced in winter when the hours of daylight are much less than in summer. A backup generator is also often used to supplement the solar energy in winter.
Grid-tied systems are directly connected into the local power distribution system. Electricity produced by the solar panels flows into the homes existing electrical system. After the home has used any of the power it requires at any given moment, excess energy then automatically flows out through your power meter and onto the grid where it becomes a part of the energy mix your neighbors are using. In Alberta this excess energy must be credited to you by your energy retailer at the same rate at which they charge you for incoming energy. Grid-tied systems require no batteries as the home can draw from the grid during the times when the solar panel is not producing electricity. An important thing to note is that if the grid goes down, the solar system also automatically shuts down for the safety of Linesmen that could be out repairing a line that they expect to be de-energized. Grid-tied solar is very efficient as there is no wasted energy. Any energy you do not use goes out to the grid and generates credits that you can use at night or in winter when your system does not produce as much.
Hybrid systems typically have a standard solar array but a smaller energy storage system than off-grid. These small battery systems can back up critical loads in the home such as a gas furnace fan, refrigerator, and a few lights. Although purchasing fewer batteries is cost saving, they don’t have the capacity to deliver peak power needs of the homeowner that an off-grid system would. This is just a safety net to keep critical electronics running during short outages.
What are the advantages and disadvantages of off-grid versus grid-tied systems?
Grid-tied systems typically have the advantage over off-grid options. First, they cost much less, as they don’t require costly energy storage battery systems. Flooded-acid batteries need to be replaced every five to ten years at significant cost. They also require regular maintenance to keep the battery healthy. Alternatively, a buyer can invest in top quality lithium batteries that don’t require regular maintenance but cost a significant amount more than flooded-acid batteries. Grid-tied systems do not have “down time” for power since the network provides electricity regardless of whether the sun is shining. One thing many people don’t realize is just how much energy they use day to day. To enjoy normal household electrical demand, including air conditioning and electric heat, an off-grid homeowner would require a sizeable, and expensive, storage system to maintain the same lifestyle. Meanwhile, with Grid-tied systems don’t require lifestyle changes as the system will automatically draw from the grid when needed.
However, off-grid systems have a place as the best or the only option sometimes. For remote locations, it may be quite costly to run power from the major power line to site. There may not even be access to the power grid. While power rates may vary in conventional connected homes, the only cost fluctuations for off-grid applications are those in the batteries and other materials used to generate, store, and distribute power.
Hybrid systems are ideal if your local grid has frequent power outages or if you have critical infrastructure that cannot handle a power outage. It is possible to add batteries to a standard grid-tied solar system in the future if it isn’t in the budget at the start.
All three systems, counterintuitively, are more efficient in cooler climates, since the ability of each cell to produce electricity drops in hot environments or where the panels heat beyond a certain temperature. In fact, when sizing wiring for solar in Northern Climates care must be taken to account for the increased voltages during extreme cold.
What lifestyle changes do I need to make with solar energy?
With a grid-tied solar system there are no lifestyle changes required. Solar panels come with 25 year performance warranty and have no moving parts to maintain.
Off-grid systems require regular maintenance of batteries and careful management of your energy consumption. Because the systems must supply all the electricity requirements of the home, the initial capital outlay includes a large amount of extra solar panels. A backup generator is also used to ensure power is provided even if there are multiple days of cloud cover when your solar may not keep up with demand.
Off-grid systems generally cannot provide sufficient power for high-draw appliances like hot water heaters, electric heating, or clothes dryers. Major appliances are typically converted to natural gas or propane in order to keep the battery bank and inverter costs down. This means that off-grid systems require significant lifestyle changes as well as planning out when power will be drawn.
What do PV systems cost?
The cost of your photovoltaic solar system depends on your annual energy consumption. Planning a system based on your lifestyle determines the size and type of system needed, as well as the materials used. After capital cost, the second element of evaluating your system cost is comparing the operating cost. Compare the cost of a PV system over its lifetime to the cost of a conventional system over the same timeline. Frequently, people compare costs of conventional systems versus alternative systems disproportionately, ignoring lifespans of each type, ongoing upgrade and maintenance costs, fluctuations in fuel or commercial power costs, or potential to use more advanced technologies and equipment with new “green energy” systems.
Calculating payback time
“Actual payback time” is the time, in years, that is needed to recover the cost of your power system. For instance, if your high-efficiency natural gas furnace costs $5,400 and you save $600 per year in energy costs per year, payback time will be nine years. That calculation ignores the fluctuating cost of natural gas.
However, if you have a system that now needs more maintenance, you should incorporate that cost into your calculations of payback as well.
A rule of thumb is that you will likely spend the same amount of money on your power bill over a period of ten years as purchasing grid-tied solar. You do not really have a choice whether you will spend this money, the choice is rather where will you spend it. If you invest that money in solar, not only does it earn its cost back well within the warranty period of the solar panels, but you also now own an asset that adds resale value to your home.
Grants and loans
In Canada we have the Canada Greener Homes Grant that will cover up to $5,000 of the cost for grid-tied solar at your primary residence. There may also be municipal or farm programs that you could be eligible for. Contact our team for more information.
Which system design is best for me?
Determining whether to install a grid-tied, off-grid, or hybrid solar system should be undertaken in consultation with our design experts. Cost and budget, frequency of use, your location (geographic and relative to power grids), lifespan of the facility, your future plans, and your lifestyle all play a role in determining the design of your photovoltaic solar energy system. Like buying a vehicle, where a truck is ill-suited for urban commutes and a subcompact makes a poor truck, finding the best way to meet current and future needs should be integral to designing the system.
Why grid tie is the most popular option.
Grid-tie systems are the most cost-effective solar solution that allows you to reduce your carbon footprint, reduce your power bill, and increase the value of your home without any maintenance requirements or lifestyle changes.
However, grid-tied systems do not provide power when the utility company needs to work on the lines or where general system power failures occur. Hybrid system with a small storage system with an automatic transfer switch that isolates your home from the grid during a power outage. It allows you to turn to the batteries for backup power.
Grid-tied and hybrid systems can be expanded when desired, producing more power if demand increases. Off-grid can also be expanded but increases to these systems will require additional storage capacity and there may be more considerations. Care must be taken as you typically do not want to mix new and old batteries as the old batteries will quickly draw the new ones down to same condition as the old.
The primary advantages of a grid-tied system is initial capital cost is much lower than the alternatives, this system is efficient as no energy is wasted, and it is virtually maintenance free.
What is involved with designing and installing my system?
Our team of specialists will guide you through the entire process of choosing, designing, and installing your system. We will look at your existing power bill to determine how much annual energy your home consumes. Next, we use satellite imagery to see how many solar panels can fit on your roof. With grid-tied solar, even if your roof cannot fit a lot of panels, you can install solar to offset a portion of your annual electricity.
Other considerations may be the roof pitch or azimuth in regards to the sun as well as shading from trees or other buildings. South facing roofs will produce the most energy, but East and West work as well.
Our team manages all the permitting and interconnection requirements and walks you through each step of the process.
You can sit back and relax while our experienced team installs your turn-key solar system from start to finish.
Do you have more questions about solar?
Are you ready to take control of rising energy prices and secure your future?
Contact our team today and we would be happy to help!