The Energy Matrix
A Science Ebook e-zine
Summer 2007 Edition  
List of all editions

The Synchronous Inverter Problem

The energy matrix examines the full spectrum of future energy sources and associated problems.  It is meant to be a thought provoking publication for students who will be our future technocrats, engineers, and physicists.  We will include concepts such as solar, DG, CHP and concepts that are not practical today such as ice engines.  Send Comments to




Micro Power Distributed Generation 
The Synchronous Inverter Problem 

As solar electric panels gets cheaper, the question "What to do with the DC power they generate and what do when the sun don't shine, becomes an important question. The most economical solution is to simply sell solar power to the electric company during the day and buy it back at night. To do this a synchronous inverter costing $2000.00 plus is required to convert the DC power to 60 hertz synchronized and phase locked to the utility grid power.  

The editorial below and the GIF animations to right suggests that a DC grid (separate wire) should be added to utility power poles to collect power from all solar and other micro power producers and sent back to a very large inverter owned by the power company.  This could eliminate hundreds of micro power inverters and replace them with one large utility inverter or a motor generator if the utility prefers. The article below is intended for physics, technical, and engineering students (grade 11 - 14) 

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to continue reading this article.

Micro Power Generation
Simple  DC to Utility Interface

This article and animation (center column investigates the feasibility of a separate DC grid for delivering electricity from home or farm micro power systems to the local electric utility. The resistors in simulation represent line resistance (.2 to 1.2 ohms). Line resistance was assigned during simulation setup but values are not shown.  The Wind, Solar, and Cogeneration or Mini Hydroelectric power inputs to the grid are constant current generators. The Hexagon with the arrow indicating current direction is a CAD software symbol for a current generator. 

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Corn Solar Collectors
Follow Up Article

In our last issue Corn Solar Collectors article, I included some rough calculations showing that silicon solar collector farms collect far more solar energy. Reference A compares switchgrass cellulose based ethanol production to solar panels.     

Reference A

Note: All arguments with respect to ethanol versus solar cell technology imply the future existence of electric cars and a power grid for electric cars.  For example electricity for cars should be made available at all US Freeway rest stops.


Japanese CHP for Home

Japan has over 15,000 Combined Heat and Power (CHP) units installed in Japan as of 2006. The Honda Micro-CHP system combines a 95% efficient natural gas furnace or boiler  with the 85% efficient Honda natural gas engine/generator module.  The generator module has a 1 kwHr output.

Reference B


Index for all Editions


Combined Heat & Power (CHP) 

DC Power Grid

District Cooling

Ethanol Viability

Hybrid Cars

Ice made with Coal

Ice Energy Density versus Battery

Heat Storage


Nuclear Energy

Solar Heat Storage in CO2

Solar Heat Storage in Water

Storing Carbon Dioxide

Stoves - Corn Burning

Stoves - Wood Pellet Burning

Stoves - Coal Burning

Tar Sand Oil


Yucca Mountain

Substituting Coal for Diesel

Compact Fluorescent Lights








Micro Power Generation
The Synchronous Inverter Problem 

You may think that only the few people with solar farms or collectors could benefit from a direct current network for collecting Micro Power electricity.  This is not necessarily true.  Every person who uses gas or even oil could be a beneficiary of micro power.  Today, many users of gas and electricity are saving money by a process called cogeneration or Combined Heat and Power (CHP). 

"However, an inverse technology is taking hold even in the USA.  Rather than produce power and sell the heat.  Many  facilities are producing heat and hot water and selling the electricity back to the electric utilities.  One method is to use gas turbines to generate electricity and  than heat water or air with the turbine exhaust.  Excess electricity is sold back to the electric company via the existing power lines.  Utilities that sell both gas and electricity are promoting this technology." from Winter Edition of The Energy Matrix.

Today CHP is used in Hospitals, Office Buildings and apartment houses but not in single family homes.  The interface to the power grid alone could cost several thousand dollars.  An Inverter required to produce synchronous 60 Hertz  costs over $2000.00.  The utilities would require that micro power system would automatically disconnect to prevent shorting or reduction in the quality of the the power on the grid.  Micro Power might be required to disconnect from the grid whenever voltage surges, spikes, or sags occur on the grid.  This is why some people feel a separate grid or wire be added to power system to collect power from CHP or solar systems.  The animation created with simulation software shows a DC collection system collecting power from 16 micro power  sources.  The system demonstrates the very stable operation of a DC collection system.   

The simulation purpose is only to provide graphics for this e-zine.  Making a simulation of a grid is the job of electrical engineers, the utility, and the Department of Energy.  I hope electronics students find it educational.    

I believe that a gas turbine or thermoelectric water heater system could be manufactured that not only heats water but also produces DC electricity. One system would use a  turbine/dynamo and the other would use  thermocouples to produce electricity.  Let us assume that the turbine/dynamo of furnace produced a  thousand watts while heating home, and the thermocouple of water heater  produced 500 watts at times dependent on hot water usage.   Small quantities of electricity such has these would not justify an expensive synchronous Inverter interface.  Actually the DC concept requires no interface at all, electrical output could be routed up alongside the jiminy to a roof mounted junction box.  The power company could take it from there.  The interface specifications would only be between the manufacturer of water heater or furnace as the case may be and the utility company.  The same DC interface could be used to interface solar power to the grid. 


Reference 1     Reference 2     Reference 3     Reference     Reference 5     Reference 6     Reference7      Reference8     Reference9         

Ref 10  Distributed Utility Integration Test

Ref 11 Consortium for Electric Reliability Technology Solutions (CERTS)














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