Solar Terminology and Definitions July 11th, 2024 Introduction to Solar Energy Solar energy is a renewable power source that’s becoming increasingly popular among New Zealand homeowners. By harnessing the sun’s energy, you can reduce your electricity bills and lower your carbon footprint. However, the world of solar energy comes with its own set of terms and concepts that might seem daunting at first. This guide aims to demystify some of the most common solar terminology, helping you make informed decisions about adopting solar power for your home. Common Solar Terms and Definitions Photovoltaic (PV) The conversion of sunlight directly into electricity using semiconducting material. Solar panels use the photovoltaic process to generate power. Solar Panel A panel designed to absorb the sun’s rays and convert that into a useful source of energy, generally either electricity or heating; PV, or photovoltaic, solar is often used to refer to a system where the panels produce electricity. Inverter A device that converts the direct current (DC) electricity produced by solar panels or discharged from batteries into alternating current (AC) electricity used in homes. Some inverters can also convert AC to DC to allow the charging of batteries from an AC source such as a generator or the grid, these are called inverter chargers. Current A flow of electrical energy (technically usually electrons). Electrons need a conducting material or space through which to travel. Diode A device through which electrical current can move freely only in one direction. Electron A subatomic particle having a negative charge. Semiconductor A crystalline substance having electrical conductivity somewhere between a conductor and an insulator. Silicon is a commonly used semiconductor in solar cells. Silicon A non-metallic element often used as a semiconductor in solar cells. Understanding Solar Power Systems Grid-Tied System A grid-tied solar system is connected to the local electricity grid. It allows you to draw power from the grid when needed and (usually) feed excess power back into it. Off-Grid System Off-grid, or grid-free solar is a standalone system not connected to the electricity grid. It requires battery storage to provide power when the sun isn’t shining and usually has a ‘back-up’ power source, such as a generator. Hybrid System A grid-tied system that incorporates energy storage system (99% of the time, a battery) allowing the use of PV solar generated power when the sun isn’t shining and also provides back-up power during a grid outage, offering greater independence and energy security. Solar Energy Components Solar Array A collection of multiple solar panels working together to generate electricity. Battery A device that stores excess energy produced by your solar panels for use when the sun isn’t shining or during power outages. Batteries come with different ‘chemistries’. You’ll often hear about the likes of lead acid, lead carbon or deep cycle batteries (a particular lead acid battery construction). Now, lithium-ion batteries are generally considered the best solution for home or commercial battery storage with the two common chemistries being lithium iron phosphate (LiFePO4) and lithium nickel manganese cobalt oxide (LiNiMnCoO2 or NMC). Solar Charge Controller A device that optimises the output of the solar panels using a maximum power point tracker (MPPT) to vary the voltage and current from the panels to optimise the output of the panels. The solar charge controller then regulates the voltage and current going to the battery (or inverter), preventing overcharging and protecting the battery from damage. Solar Panel or Module Solar panels consist of a group of PV cells electrically connected and packaged in one frame. How Solar Power Works Solar power is used to refer to the process of harnessing usable energy from the sun such that it can be used to as a utility. Solar panels are made up of photovoltaic (PV) cells, typically composed of silicon. When sunlight hits the silicon, it causes electrons to break free from their orbit around the nuclei of the silicon atoms. This creates a flow of electrons, or an electrical current. The electric field surrounding the solar cells acts as a diode, allowing electrons to flow in a certain direction. By using metal contacts on the top and bottom of the cells, it is directed that current for use outside of the panel. Energy Storage A solar power system often requires an energy storage unit called a battery to use the energy obtained throughout the day. The charge controller ensures that the batteries are not overcharged during the day or drained too much at night. To protect the battery from damage, the controller will not allow more current to be drained once the battery has been depleted to a certain level. Measuring Solar Energy Kilo (k) A kilo is “one thousand”, as in kilometre. Watt (W) A measure of power equal to a Joule (J) per second (s) (1W = 1J/s). A Joule is a measure of energy, defined by James Prescott Joule as the energy used to accelerate a body with a mass of one kilogram using one newton of force over a distance of one meter. Hour (h) The measure of time you know well. Kilowatt (kW) So kW is 1000 Watts, a measure of power. The size of a solar system is defined by its peak power, often denoted as kWp (the p standing for ‘peak’), e.g. a 1 kWp system can produce 1 kW of power per hour when operating in line with the ‘standard test conditions’. Kilowatt-Hour (kWh) kWh stands for kilowatt-hour; a kWh is a measure of energy (not power). This is what your power retailer charges you for in your power bill as it is the amount of energy you have used in the month. If your solar panels (for example) continuously output 1kW of power for 60 minutes, they will have produced 1 kWh of energy. The amount of electricity you use (or generate) is defined in kWhs. e.g. “My solar system produced 4 kWh of electricity today!” So at the highest level: kW measures power, and kWh measures energy. Peak Sun Hours The average number of hours per day when solar irradiance reaches an average of 1,000 watts of electricity per square metre. Solar Energy Policies and Incentives in New Zealand Distributed Generation The policy that allows small-scale electricity generation, like rooftop solar, to be connected to the national grid. Feed-in or Export Tariff The rate at which your electricity retailer buys back excess electricity generated by your solar system. Renewable Energy Target New Zealand’s goal to generate 100% of its electricity from renewable sources by 2030. Frequently Asked Questions What is the average payback period for a solar system in New Zealand? The payback period varies depending on factors such as system size, design, electricity usage, and local sunlight conditions. On average, it ranges from 7 to 13 years. Do solar panels work on cloudy days? Yes, solar panels can still generate electricity on cloudy days, although at a reduced efficiency compared to sunny days. How long do solar panels typically last? Most solar panels come with a 20 to 30-year warranty (our Phono Solar panels have a 30-year performance warranty) and should continue to produce electricity for 30 years or more, albeit they do experience some degradation over time. What is the role of semiconductors in solar panels? Semiconductors, typically made of silicon, are the core materials in photovoltaic cells. They allow the conversion of sunlight into electrical energy through the photovoltaic effect. Conclusion Understanding solar terminology is crucial for making informed decisions about adopting solar energy for your home. As solar technology continues to advance and become more affordable, it’s an increasingly attractive option for New Zealand homeowners looking to reduce their energy costs and environmental impact. We encourage you to continue exploring solar energy options and contact your local solar providers to determine the best solution for your home. Remember, investing in solar power is not just about immediate savings—it’s a long-term commitment to sustainable living and energy independence. — This article was first published in 2018 COMMON TERMS Current – a flow of electrical energy Diode – a device through which electrical current can move freely only in one direction Electron – subatomic particle having a negative charge Inverter – a device capable of converting electrical energy from DC to AC or vice versa. Photovoltaic – produces electrical voltage when exposed to light Semiconductor – a crystalline substance having electrical conductivity somewhere between a conductor and an insulator Silicon – a nonmetallic element used often as a semiconductor BASICS Solar power is the technology of harnessing usable energy from the sun. Solar panels are made up of photovoltaic (PV) cells. A module is a group of cells electrically connected and packaged in one frame. PV cells are composed of special materials called semiconductors, most commonly silicon. When energy in the form of heat from the sun is added to the silicon, it causes electrons to break free from their orbit around the nuclei of the silicon atoms. These atoms are left with a positive charge, while the electrons carry a negative charge. The electrons, or free carriers, carry an electrical current. The free carriers roam around until they find atoms lacking an electron and then fall into the orbit of these atoms. The electric field surrounding the solar cells acts as a diode allowing electrons to flow in a certain direction. This flow is an electrical current. When using metal on the top and bottom of the cells, we can direct that current to be usable outside of the panel. ENERGY STORAGE A solar power system requires an energy storage unit called a battery in order to use the energy obtained throughout the day. The use of batteries requires a charge controller. The charge controller ensures that the batteries are not overcharged during the day or drained too much at night. Once the battery has been drained down to a certain level, the controller will not allow more current to be drained in order to protect the battery from damage.
