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Differences in Solar Kits (Grid-Tied, Off-Grid, Hybrid)

Grid Tied Solar Kits

Grid-tied, or often called on-grid solar kits, are solar PV systems that are connected to the National Power grid.

Grid-tied solar system

Advantages of Grid-Tied Systems

A grid connection will allow you to save money with solar panels through better efficiency rates, the export tariff (SEG), plus lower equipment and installation costs:

Batteries, and other stand-alone equipment, are required for a fully functional off-grid solar system and add to costs as well as maintenance. Grid-tied solar systems are therefore generally cheaper and simpler to install.  With our DIY Plug-In Solar Kits, you can install a Solar Kit yourself, with no training required.

 

The national grid is a virtual battery

Electricity has to be used in real time. However, it can be temporarily stored as other forms of energy (e.g. chemical energy in batteries). Energy storage typically comes with significant losses.

The electric power grid is in many ways also a battery, without the need for maintenance or replacements, and with much better efficiency rates. In other words, more electricity (and more money) goes to waste with conventional battery systems.

According to EIA data[1], national, annual electricity transmission and distribution losses average about 7% of the electricity that is transmitted in the United States. Lead-acid batteries, which are commonly used with solar panels, are only 80-90% efficient at storing energy, and their performance degrades with time.

Additional perks of being grid-tied include access to backup power from the utility grid (in case your solar system stop generating electricity for one reason or another). At the same time you help to mitigate the utility company`s peak load. As a result, the efficiency of our electrical system as a whole goes up.

Equipment Required for Grid-Tied Solar Systems

There are a few key differences between the equipment needed for grid-tied, off-grid and hybrid solar systems. Standard grid-tied solar systems rely on the following components:

  • Solar Panels
  • Grid-Tied Central Inverter or Grid-Tied Micro-Inverters
  • Mounting System

Grid-Tie Inverters

What is the job of a solar inverter? They regulate the voltage and current received from your solar panels. Direct current (DC) from your solar panels is converted into alternating current (AC), which is the type of current that is used by the electrical appliances in the home.

In addition to this, grid tied inverters, synchronize the phase and frequency of the current to fit the utility grid (nominally 50Hz). The output voltage is also adjusted slightly higher than the grid voltage in order for excess electricity to flow outwards to the grid.

Micro-Inverters / Central Inverters

Micro-inverters go on the back of each solar panel and convert the energy from each individual solar panel, as opposed to one central inverter that converts all the energy from all the solar panels.

Micro-inverters are more expensive in larger systems, but in most cases yield higher efficiency rates. Homeowners who have shading issues should definitely use micro-inverters, or panel optimisers to ensure the best performance from their solar kit.

Off-Grid Solar Kits

An off-grid solar system (standalone) is the obvious alternative to one that is grid-tied. For homeowners that have access to the grid, off-grid solar systems are usually out of question. Here’s why:

To ensure access to electricity at all times, off-grid solar systems require battery storage and a backup generator. On top of this, a battery bank typically needs to be replaced after 10 years. Batteries are complicated, expensive and decrease overall system efficiency.

However if you have no access to the utility grid,Off-grid solar power kits can be cheaper than extending power lines in certain remote areas.  Energy self-sufficiency is also a form of security. Power failures on the National grid do not affect off-grid solar systems.

On the flip side, batteries can only store a certain amount of energy, and during cloudy times, being connected to the grid is actually where the security is. You should install a backup generator to be prepared for these kinds of situations.

Equipment Required for Off-Grid Solar Systems

Typical off-grid solar systems require the following components:

  • Solar Panels
  • Solar Charge Controller/Off-Grid Inverter
  • Battery
  • Backup Generator (optional)

Solar Charge Controller
Solar charge controllers limit the rate of current being delivered to the battery bank and protect the batteries from overcharging.

Good charge controllers are crucial for keeping the batteries healthy, which ensures the lifetime of a battery bank is maximized. If you have a good Off Grid inverter, chances are that the charge controller is integrated.

Battery Bank
Without a battery bank (or a generator) it’ll be lights out by sunset. A battery bank is essentially a group of batteries wired together to provide power when there is no sunlight.  Batteries are available in many different forms, such as Lithium Ion, AGM or LifePO4.

Off-Grid Inverter
Off-grid inverters do not have to match phase with the utility sine wave as opposed to grid-tie inverters. Electrical current flows from the solar panels through the solar charge controller and the bank battery bank before it is finally converted into AC by the off-grid-inverter.

Backup Generator
It takes a lot of money and a big battery bank to prepare for several consecutive days without the sun shining (or access to the grid). This is where backup generators come in.

In most cases, installing a backup generator that runs on diesel is a better choice than investing in an oversized battery bank that seldom gets to operate at it’s full potential. Generators can run on propane, petroleum, gasoline and many other fuel types.

Backup generators typically output AC, which can be sent through the inverter for direct use, or it can be converted into DC for battery storage.

You can check out our Off-Grid Solar Kits here: https://www.pluginsolar.co.uk/?product_cat=complete-off-grid

 

Hybrid Solar Systems

Hybrid solar systems combine the best elements from grid-tied and off-grid solar systems. These systems can either be described as off-grid solar with utility backup power, or grid-tied solar with extra battery storage.

Hybrid solar system

Advantages of Hybrid Solar Kits

Less expensive than off-gird solar systems
Hybrid solar systems are less expensive than off-grid solar systems. You don’t really need a backup generator, and the capacity of your battery bank can be downsized. Off-peak electricity from the utility company is cheaper than diesel.

Hybrid Solar is the Future
The introduction of hybrid solar systems has opened up many interesting innovations. New inverters let homeowners take advantage of changes in the utility electricity rates throughout the day.

Solar panels happen to output the most electrical power at noon – not long before the price of electricity peaks. Your home and electrical vehicle can be programmed to consume power during off-peak hours (or from your solar panels).

Consequently, you can temporarily store whatever excess electricity your solar panels in batteries, and put it on the National grid when you are paid the most for every kWh.

Equipment Required for Hybrid Solar Systems

Typical hybrid solar systems are based on the following additional components:

  • Solar Panels
  • Grid-Tie Inverter with Battery Manager and Charge Controller (known as Hybrid Inverters)
  • Battery Bank

Hybrid Inverters
Hybrid solar systems utilize battery-based grid-tie inverters. These devices combine can draw electrical power to and from battery banks, as well as synchronise with the National grid.

Using a Hybrid Solar System, any surplus energy generated from the solar panels during the day will be used to charge the batteries, allowing the use of this energy later in the day when the solar panels aren’t generating. This allows the utilisation of energy generated from the photovoltaic system rather than drawing from the grid during peak times. The Hybrid Kit is also intelligent, with built-in export limitation and AC output limitation in response to grid frequency and voltage extremes.

You can see our range of Hybrid Solar Kits here: https://www.pluginsolar.co.uk/?product_cat=on-roof-tile-slate-hybrid-solar-kits

Source: EnergyInformative.Org