WHAT IS A PURE SINEWAVE ,MODIFIED SINEWAVE , GRID-TIED, OFF-GRID AND HYBRID INVERTER? DIFFERENCE??
- rentechsyst
- Jun 11, 2020
- 3 min read
Updated: Jul 20, 2024
There are a lot of different inverters out there of different shapes and sizes and types. But which one is the best for me, you might ask?
When solar panels produce electricity it comes from the panels to the system as Direct Current (DC). If the system has battery storage, the panels will also charge the batteries, via the charge controller, and the energy is stored and delivered as direct current. The only problem with this is that most domestic and commercial appliances (TVs, Fridges, fans, lights) operate using what is called Alternating Current (AC). The inverter (technically actually a converter) comes to solve this problem and converts direct current (from panels and/or batteries) to alternating current that can be used by appliances.
Pure Sine-wave vs Modified Sine-wave?
So what is the difference between a pure sine-wave inverter and a modified sine-wave inverter?? Both inverters convert DC to AC and produce a sine-wave form of current, with difference being in “purity” of the sine-wave. The wave from pure sine-wave inverters is more pure and refined compared to modified sine-wave inverters (see Fig 2 above). Pure sine-wave inverters produce electricity of the same form as what we get from the grid (ZESA). Because of the purity of the sine wave from Pure Sine-wave inverters, there are no distortion or disturbance issues at the appliances2. However with modified sine-wave inverters, there can be some distortions or disturbances, in the worst case some appliances simply won’t turn on or work.
In terms of cost, modified sine-wave inverters are cheaper and are usually recommended for areas (like most rural areas) where the range of appliances being used does not have too many advanced electronic components, with tests done for certainty of functionality. For guaranteed performance, a pure sine-wave inverter is always recommended.
OFF-GRID vs GRID-TIED vs HYBRID Inverters
Another common classification of inverters is by range of application:
(i) Off-grid (sometimes called “stand-alone”) inverters - these are the most common inverters in Zimbabwean households. These are used in a system where batteries are charged using solar panels, and in some instances electricity from the grid (ZESA) is used to replenish (top-up) the batteries. This type of INVERTER is not tied to the grid, meaning it does not have the function of sending electricity to the grid in periods of excess power production. These inverters can provide back-up power in periods where there is no electricity from the grid (ZESA)
(ii) Grid-tied inverters: these types of inverters- this type of inverter converts electricity from the panels and either sends it straight to appliances or to the grid if there is excess power produced. They can send electricity to the grid because they have the capability of matching the phase of power produced to the one supplied by the grid. These inverters are designed to shut down in the event of loss of electricity from the grid for safety reasons…. And as such they do NOT provide back-up power to appliances3.
(iii) Hybrid Inverters: this type then combines the off-grid and grid-tied inverter functions. These inverters can work in off-grid mode, and also tied to the grid, meaning that, during the day, in the event of production of excess energy, this energy can be “pumped” back to the grid.. and they also allow back-up power in the event of power outage. Because of this combined function, these are generally the most expensive inverters on the market.
Can I have an inverter without solar panels and expand later??? – Yes!! Absolutely you can! If your home is connected to the grid, you can charge your batteries with electricity from the grid (ZESA) using the inverters (those with a grid-charging function). You can always hook up your panels at a later stage… with proper sizing and matching of-course.
And again those 2 important questions should be asked after considering all those types and classification for your final decision:
(i) Which are the good brands available??.- quality of products (ii) Who will install my system??- quality of design and workmanship.
SOURCES:
1. https://www.altestore.com/blog/wp-content/uploads/2015/10/modified-sine-wave-vs-pure-sine-wave.jpg
About Author:
Lovewell Chitiyo is a Mechanical Engineer with 15 years experience in the building services Engineering consultancy, renewable energy systems and sustainable design fields. He is currently studying Masters in Renewable Energy at Stellenbosch University in South Africa
Lovewell is an Accredited Professional with the Green Building Council of South Africa for Existing Buildings Performance and New Buildings; Interiors, holding several qualifications and certification in Renewable Energy and Sustainability.
Lovewell also has vast experience in design, supervision, installation and commissioning of several projects locally and regionally in the last 15 years.
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