Grid-Tie PV System VS Off-Grid PV System

There are basically three types of solar PV systems existing today for solar power generation at home, including grid-tie, off-grid and hybrid PV systems. However, as expense and efficiency are concerned, grid-tie and off-grid systems are more popular and most installed around the world. Now let’s compare them with each other and help you decide which system should be suitable for your house.

grid-tie solar PV system
grid-tie solar PV system

Grid-Tie System

1. This installation requires your system is connected to the local national (utility) grid.
2. After the connection, the system can feed the electricity (usually extra electricity) it generates to the national grid (this helps it earns money from the grid), and your home can get the electricity from the national grid once your system stops generating electricity at night or in special conditions.
3. The current form your solar panels generates is direct current (DC), which must be converted into alternating current (AC) for home use by going through a PV inverter. The current converted by the inverter must be compatible with the voltage of the local grid.
4. The inverter also needs to be a grid-tie type. An off-grid one cannot be used here.

Off-Grid System

off-grid PV system
off-grid PV system

1. Off-grid means the system is disconnected from the local national grid and cannot feed extra electricity to earn money.
2. This installation needs storage batteries, which usually cost a lot of budget.
3. This system is suitable for installation in areas where houses cannot be connected to the national grid or where residents are far away from grids and cities.
4. It needs a charge controller which is used to charge the batteries of the system.
5. The DC from solar panels usually goes to a battery and then to an inverter.
6. This inverter is an off-grid inverter.

Grid-Tie Advantages

1. It can constantly power your house unless the national grid is down and the system meets its special conditions.
2. It can help earn money from the local government by selling extra electricity.
3. It costs less compared with an off-grid system because it doesn’t need expensive batteries.
4. It works more efficiently because its DC doesn’t to go into a battery. This process causes energy loss.

Off-Grid Advantages

1. It can be used in remote areas where national grids cannot reach.
2. It can store extra energy and use it whenever your house needs.
3. It doesn’t need the grid-connecting process.
4. It is totally environmentally friendly.

Current Condition

In comparison, residents around the world prefer a grid-tie system more, and many countries like the UK, the US, the Netherlands and China are encouraging their residents to install this system. But In India, an off-grid system seems to enjoy more welcome because many regions in the country cannot reach national grids.


Chinese New Energy Company Releases New Solar Inverters for Distributed PV Power

Omnik New Energy
Omnik New Energy

Omnik New Energy (Omnik for short), a Chinese-German joint venture has released a new series of solar inverters. Its new products include single phase, three phase and hybrid inverters. By launching these new products, the solar energy company aims to help develop the distributed solar PV (photovoltaic) industry which is expanding across the globe.

These newly-launched products have capacities ranging from 1 kW to 20 kW, and their difference from traditional inverters is that they don’t need transformers except for one single phase inverter specially made for Japanese users. These products are specially designed and manufactured for residential and commercial solar PV systems which are known as distributed PV power systems.

Aiming to expand its UK solar market, the solar energy company also participated in the Ecobuild 2015 exhibition held in London from March 3 to 5, 2015. During the three days in London, the general manager of Omnik Franz Zhao appeared and communicated with those who visited its booth for relevant information consultation. At the exhibition Omniksol-2k-TL2, Omniksol-3k-TL2-S, Omniksol-1k-M and other newly-launched inverters were displayed.

Headquartered in Suzhou, China, Omnik is an innovative high technology solar company, specializing in R&D and manufacturing and marketing PV inverters, with offices in the UK, the Netherlands and Australia. Outside China Omnik mainly focuses on selling inverters, while in China the company sells inverters and builds distributed solar PV systems for local customers.

Contact the company
Address: bioBAY Park A4-414, XingHu St. No.218, Suzhou, Jiangsu, China
Postal code: 215123
Tel: +86-512-6956-8216
Fax: +86-512-6295-6682

How to install and maintain your PV system?

home PV system
home PV system

How do install a home PV system? This is a question always asked and concerned about by those who wish to go solar. But others think this is not a big issue because installers will help you solve the problem. My answer is you had better learn something about it.

First, you should make your self clear that your community permits this. I have heard that some communities don’t approve this. So, making sure of this will save lots of your energy.

Second, before the solar panels are transported to your home, you need a slant rooftop with an area of at least 30 square meters. The rooftop had better be a slope with a certain angle, for this is the best for absorbing sunlight. If you don’t have such a rooftop but only a flat one, you need racks to support your solar panels with such an angle. Or if you don’t think installing panels on your rooftop is possible, you can also ask the installer to install them on the ground to which you own the property right.

Third, when your panels arrive, you may pick out a spot on your rooftop or ground to install them properly. No matter whether you install them on your roof or on the ground, you should make sure they face south, east or west, so that they can catch the most sunlight and generate the most direct current.

Fourth, install some racks on your roof or on the ground to fasten solar panels. After this process you can install the panels on them in the angles that suit your local latitude condition the most.

After the installation, you may connect your panels to the solar inverter or microinverters for the sake of converting direct current into alternating current. Finally, connect your whole PV system to the local utility grid. If you are intended to do so, you may also need to install the prepared batteries into the system to satisfy the constant power supply for your house. Some who have enough financial support can connect to the grid and install batteries.

Once the installation job is over, you must be considering how to maintain it. To be honest, such a system doesn’t need too much of your time for its maintenance. You only need to make sure the panels are always clean, without anything like bird droppings, dust or snow on them. Three or four times of cleaning in a year is enough, unless you meet special extreme conditions. In addition, make sure your solar inverters are free from dust and moisture.

The PV power system and its working principle

omnik solar power system
omnik solar power system

What is a PV power system?
It is a system which consists of solar panels, power-charging and -discharging controllers, a solar inverter, a tester, and other computer and mobile electronic devices, storage batteries, and other assistant power geenration devices. It works to generate electricity by absorbing sunlight and converts it into home use electricity.

What are advantages of the system?
1.It doesn’t have moving components that often produce lots of noise. It is home-friendly.
2.It is environment-friendly and will never emit polluted air or water.
3.It doesn’t need a procedure which needs biofuels to power itself.
4.It is easy to repair and maintain, and so you don’t have to spend so much money on its repair and maintenance.
5.It is reliable and stable.
6.The solar panels all have a long lifespan and they often span up to 25 years.
7. You can easily expand your scale of power generation according to your individual demands.

Use of the PV power system
It is now a widely used system that can be generally divided into two types: stand alone and grid-tie power generation systems. So far, developed countries such as the UK and the US have begun to install the grid-tie power system in their cities. China and Japan are now following this fashion too. They are mainly building residential rooftop PV power systems and MW-level large-scale grid-tie power generation systems. It can be used in different areas, such as home, transport, communications, space and others.

Working principle
Although they have different sizes and forms, their working principle is the same. Generally speaking, it is a system that generates electricity from sunlight by its solar panels, and then charges the storage batteries through the control of the controller, or supplies the direct current load if the load requirement is satisfied. If there is no rich sunlight or if it is at night, controlled by a controller, electricity will be transmitted to the direct current load. If the electricity needs to be used in a house, the direct current must be converted by a solar inverter into alternating current.

What are grid-tie solar inverters?

grid tie inverter
grid tie inverter

Solar energy is now being used to generate electricity by numerous solar power plants scattered around the world. Solar inverters have been used to convert the direct current generated from sunlight into alternating current. Grid-tie and off-grid inverters are the two major types that are used, especially grid-tie inverters. But what are they?

Concept: Grid-tie inverters are those that turn direct current into alternating current and can synchronize to interface with a utility line. If direct current voltage is a little bit low, it will raise it by using its alternating current transformer, so as to get the standard alternating current voltage and frequency.

Requirements and features for each inverter:
1.Each inverter is required to have high efficiency.
2.Each inverter needs more reliability.
3.The direct current input voltage must be broad.
4.These inverters help each solar power system sell unused electricity to the utility grid.
5.They should be quickly disconnected from the utility grid when it is being fixed.
6.They don’t need storage batteries.

Transformer type: newer high-frequency transformer, conventional low-frequency transformer and transformerless solar inverters.

Inverter type:
Central inverters: They are often used in large-scale PV power plants (over 10kW). Their most prominent features are that each system has high power and low cost. However, they might be affected by the matching of PV modules and shading. If they are affected, the whole PV system’s efficiency and output will also be affected. Meanwhile, the reliability of the whole system is also affected by a PV unit team which doesn’t work well. The newest methods to solving this problem are two: adjusting it through space vector and developing new topography connections of the inverter.

String inverters: Based on the module concept, each PV string (1kW to 5kW) has MTTP at the direct current end and parallels and connects to the grid at the alternating current end. Lots of large-scale PV power plants use string inverters. Its features lie in that their efficiency won’t be affected by the module differences between strings and shading, and that this avoids the mismatches between PV modules’ best points and inverters. Therefore, more electricity can be generated. Today, transformerless string inverters are leaders among other kinds.

Multiple string inverters: These inverters can be installed in the PV power plants which have the capacity of thousands of MW. In addition, they have the features of central and string inverters. In these inverters, different single power peak value tracking and direct current to direct current converters are included. These direct currents are turned into alternating currents through a common direct to alternating inverter and connect to the utility grid. As the length of the direct current cable decreases, the shading between the strings and the losses caused by the distinctions between the strings will be reduced to the minimum amount.

Module inverters: They connect each module with a inverter. At the same time each module has a single maximum power peak value tracking. They are often installed in the power plants with the capacity from 50W to 400W. The total efficiency is lower than that of string inverters.