Grid Tie Inverter

The Grid Tie Inverter or synchronous inverter is a special type of power inverter that converts DC electricity into alternating current. A special feature of these types of inverters is that it can feed AC into the existing electrical grid. GTIs are often used to convert DC electricity produced by renewable sources of energy like small wind turbines using permanent magnet generators into AC used to power homes and businesses.

During the period of overproduction from the permanent magnet source, power is routed back to the state grid and hence sold to the local power corporations. But these types of arrangements are possible with special type of grid networks only. These grids are specially manufactured to allow ease of distribution and back feeding.  Residential areas and businesses connected with grid-tied electrical system are permitted in many countries most popular being North America and Europe. There are different compensating ways in which different governments pay the individuals for feeding back the power like “Net metering” or “Feed-in-tariff”. 

Due to this system, the payback period of the renewable energy source like a windpermanent magnet generator decreases and hence the inflow of money is increased for the consumer. Hence using a wind permanent magnet generator is becoming a popular way of generating the power in many nations.

More on Permanent magnet generators and grid tie inverters to come……..Keep following. 

Small Wind Industry moves towards higher kilowatts

Power generation for the small wind industry is experiencing a change. The demand for higher power turbines is increasing in many markets all around the world. Demand is moving from less than 1kw to 5kw and higher. These are generally for home purposes or businesses. Typically the speed of these 5kw horizontal wind turbines range from 200 rpm to 450 rpm at the rated output for the permanent magnet generator. Producing more power than required lets you store the excess generation in batteries which can be used whenever required or even sell the excess generation back to the state grid in countries which allow it. This is an innovative way to generate and store energy which can have low payback periods through PMGL’s wind permanent magnet generators.

Pension Funds: Latest investors in the energy sector

Wind energy companies seek to develop more and more operational wind energy projects and farms every year. Many nations have now pledged to get a major portion of their power from renewable sources of energy like wind, water etc. but funds for these projects are huge and large companies are relying less on loans from banks.

Developers of large renewable energy projects are now targeting investments from pension funds. The expansion plans of many companies and nations have clearly laid down the need of development of renewable energy projects in coming decades. For achieving these goals, pension funds look to be a good investment source since they have a lower threshold for return
on invested capital.

Latest news of Swedish wind power, Arise Windpower, indulging in such new investment plans for upcoming projects show the eagerness of investors to see renewable energy projects as a source of stable and consisting cash flow. If these institutional investors are successfully tapped, then the inflow of capital will get a boost and a long term growth trajectory can be drawn for this industry.

MPPT: Maximum Power Point Tracking 

Maximizing Power output of wind permanent magnet generators with MPPT

Maximum Power Point Tracking or MPPT is an electronic system that allows grid tie inverters and battery chargers to get maximum power from the electricity source. These sources can be solar panels or other renewable sources like wind using permanent magnet alternators. MPPT is a technique through which maximum power is obtained. For wind generators, a controller compares the output of the pm alternator and compares it with the battery voltage. MPPT changes the electrical output voltage and current levels. This available power is provided to the battery in the form of increased current. MPPT detects the optimal power that can be obtained from the system and thus makes changes in the voltage.

Example

Imagine a conventional controller (non MPPT) that connects the alternator (75W) to the battery (12V) to charge a discharged battery. This makes the permanent magnet alternator operate at the battery voltage which may not be the ideal voltage at which the module is capable of producing. The maximum power may be obtained at some other voltage point. By limiting the voltage to 12V, the 75W wind generator system is able to produce power limited to a 53W module. Hence potential is not reached.

With a MPPT system attached arrangement, the controller will detect the voltage at which the module gives its maximum possible voltage which in this example is of 17V. The MPPT system then operates the module at 17V and extracts complete 75W of power. This is irrespective of the current battery voltage.

Wind Turbine for High Speed Winds

Aviation technology has developed designs to harness wind energy at higher speeds. Modern wind turbines are developed with the motive of utilizing more and more wind that strikes the blades of the wind mill. While wind is certainly a renewable source of energy, main problem with wind is its erratic nature. Power per square meter is the cube of the wind velocity.

Wind Energy measurements:

 Kinetic energy of the wind is half of (mass * velocity squared)

Amount of energy moving past a point on the wind turbine therefore depends on the velocity.So the power per unit area comes out to be Kinetic Energy * velocity = MV³ 

Having power being related to the cube of velocity creates a large difference in generation potential for higher wind speeds.

Imagine wind blowing at 60mph gives 27 times more power than wind at 20mph.  

Wind mill efficiency: Windmills cannot have 100% efficiency since the structure itself impedes the flow of the wind. Many times the efficiency depends on the actual wind speed, in correlation to the wind speed design.

Offshore wind:

Wind energy is the most popular renewable source of energy worldwide which can meet electricity demands in a sustainable and clean way. Offshore wind is attractive since it has minimal environmental effects. Also the wind speeds at offshore areas is greater which means increased production as power is related to the cube of the wind velocity. On an average the wind speed increases by 10-20% at off shore wind farms.  But higher energy yield has to compensate the additional maintenance and installation cost. Hence the needs of modern wind turbines which can withstand higher wind speeds and perform efficiently are in great              demand. 

High Speed Wind Permanent Magnet Generator  

There is a demand for wind turbines which start producing at low wind speeds and withstand

high wind speeds too. To continually run at high speeds, foundation, tower (mount), blades, and the permanent magnet generator should be designed properly so that they are strong enough to handle the greater mechanical force and electrical output.

The energy in the wind is proportional to the cube of the wind speed, so a wind turbine operating at very high speed will be under a huge amount of stress but also have the opportunity to generate exponentially. Many manufacturers are using fewer blades for a wind turbine which are longer and can withstand higher speeds. Also windings of the permanent magnet generators should not overheat under this stress. Hence permanent magnet alternators are built to withstand higher wind speeds so that the efficiency of the wind mills is not affected and no damage is done to the internal parts of the generator. All these measures lead to the development of a turbine which withstands speeds which are higher than average. These models are essential since the power obtained from these high speed winds is enormous and should not be wasted. Power

densities are increased if we successfully utilize these high speed winds which are in abundance at many off shore and high latitude areas.