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Frequently Asked Questions - Efficiency

What's the difference between Efficiency and Efficacy ?

Why is Yield important ?

Is Renewable Energy efficient ?


What's the difference between Efficiency and Efficacy ?

Efficiency is a measure of the losses in any system.  For example, the mechanical efficiency of a gear set is related to the friction between the gears.  High friction means high energy  loss which is described as a loss in efficiency. In power electronics, high energy loss results in heat being generated.

Efficacy is a measure of the effectiveness of any system.  In our example of a gear set, high efficacy would be achieved when the gear ratios are properly selected to effectively transfer power from the input side to the output side.  If you've ever ridden a 6-speed bicycle in the wrong gear, you instantly know that a very high gear going up a hill is just not effective, and equally, a very low gear going down that same hill is equally ineffective. 

In a solar array, high Efficacy means that the system is 'up and running' for more of the day.  Thus, High Efficacy invereters will gather energy for more hours per day, while a Low Efficacy inverter will have to wait longer in the morning for the PV panels to generate enough power to 'turn it on', and will also 'turn off' sooner in the day as the light level decreases.

Please see this white paper for a discussion of Efficiency and Efficacy as it relates to Renewable Energy.

Simply put, if you are to receive the greatest return on your investment in Renewable Energy equipment, choose the equipment with the highest Efficacy.  To see the results of highly effective Power Electronics, please check out these Tech Sheets.

Why is Yield important ?

Yield ( in the Renewable Energy world ) is measured by how many kiloWatthours of electricity an installation delivers.  Yield is governed by both Efficiency and Efficacy, and both will contribute directly to annual energy capture and therefore the payback - as payback is a direct result of energy generated and either used directly or sold to the grid.  Simply put, high-yield equipment gives you more electricity for the same investment.

It is important to realize that ALL systems should be evaluated in terms of Annual Yield, which is more dependent on Efficacy than Efficiency.

Evaluation of  'nameplate rating' or 'price per kilowatt' usually results in a misleading result because such measurements are based on idealized conditions ( wind and sunshine ) which actually don't exist.  The only reasonable measurement is how many kiloWatthours are generated per year.  All Hybridyne Power Electronics calculations are based on Annual Yield.

Please be aware that not all systems are equal.  A common misconception is that "all inverters are the same", and that all renewable energy systems operate with the same basic principal.  In our opinion, there are three different ranges of  wind/solar equipment available :

  1. the "hobby kit" - these are very small, often low efficacy (low annual yield) units which you might buy at your local retailer.  They are intended to provide a little electricity for the cottage, or to reduce the electrical bill at home.  Because they are designed neither for the source ( the wind turbine or solar panel ), nor the load ( where and how the electricity is used ) , they often do not gather and store energy very  effectively.

  2. the "wind farm".  These are the very large, and often very expensive wind turbines and their ancillary equipment.  They are designed for direct connection to the electrical grid as power utilities, and they are intended to be located in areas of constant high-velocity wind. 

Conventional conversion equipment used with large wind turbines are usually unable to gather the electricity which is generated at low wind speeds, and thus do not gather much energy at the bottom end of the wind energy spectrum. The Hybridyne Power Electronics CIT will effectively and efficiently gather electricity at lower wind speeds than older technology equipment.

At high wind speeds, large turbines with older conversion equipment are typically slowed down by mechanical braking systems or "dump load resistors" which waste further available energy.  Instead, the Hybridyne Power Electronics CIT will go on gathering electricity at higher wind speeds, using the generation process as a 'brake' - further increasing the annual yield of the overall system.

Perhaps of more interest is the fact that a broader range of wind speeds at which electricity is generated means that geographic areas hitherto unsuitable for wind farms may now become good candidates.  The high wind areas ( usually coastlines, mountaintops, and strategically placed valleys ) are uncommon, and usually already contracted to wind farms using older, low efficiency technology.  The more 'normal' wind areas which are found over 80% of the globe, are now economically suitable for development of wind farms.

  1. Large "solar farms" have a similar limitation - the control systems only start gathering energy when the voltage reaches a preset threshold value, and stop gathering energy when the voltage drops back to that threshold. This often saves money in power electronics but costs money by requiring more PV panels, more land area, and/or lost efficiency.

    The use of the Patent-Pending Hybridyne Conversion/Inversion Technology ( CIT )  increases the efficacy ( and thus the energy and monetary yield ) significantly.

  2. Distributed Generation Systems - Hybridyne Power Systems ( our sister company ) builds 'mid range' systems which are designed specifically for the building load they will be supporting, even in areas of low wind or less than perfect sunlight  Therefore :

  • as soon as the high wind-efficiency turbines start to turn ( even in light wind ) the Hybridyne Conversion/Inversion Technology (CIT) starts gathering energy . ( Click here to see the difference )

  • as soon as the solar panels are illuminated, the CIT will gather whatever energy is available. ( Click here to see the difference )

  • in very high winds, where normal control systems slow the turbines mechanically, ( with brakes, by feathering the blades, or with 'dump load' resistors ), the CIT uses the load (or the grid)  as the brake - directing the extra energy into the storage system or the grid. This allows the turbine to continue to be utilized in higher than average wind speeds ( higher in the wind energy spectrum ) than would otherwise be expected.

  • later in the day, as the sun's illumination decreases, the CIT still gathers whatever energy is available - producing electricity long after conventional 'inverters' have shut down.

Is Renewable Energy Effective?
  • The efficacy of any system, including one which uses Renewable Energy to generate electricity, depends on the quality of engineering done on the equipment used.

  • Wind Turbine efficiency depends on blade design, alternator efficiency and mechanical efficiency. 

  • Solar Panel efficiency depends on ‘density” ( how much energy is generated per square metre ), and the technology of the collector. 

  • Power Electronics efficiency is a measure of how much energy is converted to heat instead of electricity

  • Storage efficiency depends on :

    • the type of battery used, (which will determine it’s output and longevity) and  

    • the Power Electronics that manages the charging and discharging of the batteries.  Hybridyne Power Electronics’s patent-pending Conversion/Inversion Technology ( CIT )  is able to use batteries very efficiently, and extends their lifespan accordingly, which reduces capital maintenance costs over time, and improves payback.

  • System Efficacy is a measure of how much of the available energy ( e.g. sunlight throughout the day ) is converted to electricity.

Generally, when describing the efficiency of any generating system ( for example , coal-fired  )  the efficacy is measured as the number of kilowatt hours generated per dollar of fuel burned.  Since the ‘fuel’ for Renewable Energy systems is free, the efficacy is very high, and therefore much more effective than any fuel-based generation system.  Beyond that, is the question of how much electricity is returned for the cost of purchase and construction.