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Course Title
100 Home
101 Introduction
102 FAQ Page
103 Course Catalog
104 Green World
105 Demand & Supply
106 Conservation Careers
107 Solar Careers
108 Wind Turbine Careers
109 Entrepreneurs
110 Employee or Employer?
200 Demand Management
201 Summary
202 Residential Energy Profile
203 Ten Conservation Rules
204 HVAC System
205 Kitchen Appliances
206 Water Heater
207 Lighting
208 Laundry Appliances
209 Calculating Savings
300 Renewable Technology
301 Solar Energy
302 Solar Collectors
303 Solar Water Heating
304 Stirling Engines
305 Basic AC-DC Electronics
306 Silicon Solar Panels
307 Thin Film Solar Panels
308 Wind Turbines
309 Inverters
310 Grid Tied and Off Grid
311 Solar Site Survey
312 Solar Site Diagram
313 Sun Path Chart
314 Site Survey Worksheet
315 Wind Turbine Site Survey
316 Wind Turbine Worksheet
400 Solar Thermal Design
401 Solar Heat Overview
402 System Configuration
403 Site Survey
404 SRCC Compliance
405 System Specification
406 Bill of Materials
407 System Installation
408 Solar Heat Incentives
409 Document Package
410 Future Products
500 Solar PV Design
501 Solar PV Overview
502 System Configuration
503 Site Survey
504 Grid Tied & Off Grid
505 System Specification
506 Bill of Materials
507 System Installation
508 Solar PV Incentives
509 Document Package
510 Future Products
600 Wind Turbine Design
601 Wind Turbine Overview
602 System Configuration
603 Site Survey
604 Grid Tied and Off Grid
605 System Specification
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Green Collar Careers - Grid Tied and Off Grid Power

Off Grid Power is for a building or system that will not be connected to the utility power grid.  While that can simplify some of the inverter complexity and utility connection red tape it also suggests that some back up system will be required when the generation system is inactive.  Usually that means batteries.

Off Grid systems generally require a more robust design for the inverter, and may even require a dual inverter system and a battery charger system. 

 

 
Grid Tied Power simplifies the overall system design because the utility power will handle the excess surges from appliances like HVAC systems or well pumps and usually there are no batteries to charge.  Some installations that have frequent power outages may choose battery back ups although less then 3% of the grid tied systems use them.

Grid Tied power has become much more readily accepted by utilities, in fact several utilities offer special bonuses for those who install grid tied renewable energy systems.  For example in Texas one utility will actually pay residential account holders over $2 per installed DC watt of panel and pay for the excess power generated by the system at wholesale rates.  For a 3000 Watt system, that translates to the homeowner receiving a $6000 check from the utility just to install the system.  So why would they do that?  The utility is buying a Carbon Credit at lower cost then they pay for commercial wind turbine Carbon Credits.

In most cases the utility will stipulate minimal specifications for the inverter, breakers, ground and lightning surge protection required for the installation.  In nearly all cases the utility will maintain a listing of qualified inverters and any other protective equipment they require.

In nearly all cases the installer will need to be certified by the utility.  That only applies to the craftsperson who makes the electrical connections not the entire system installation.

In nearly all cases the utility will buy back surplus power at wholesale rates; if through the daylight hours the system generates 6kWh and you only use 2 kWh at the same time, the remaining 4kWh is "in the bank" for you to use later at no extra cost.   However if at the end of the month you produced 100 kWh more then you consumed, they would only pay you a reduced rate of wholesale price.  Wouldn't it be nice to get a check back from the utility provider with the bill?

If the system you're designing is a Grid Tied system, the first place to begin is consulting the available utility services to see what they offer and what they require.  All options must be carefully considered for the customer in this decision as they generally will have a long term contract with the utility particularly in the event the utility purchases the Carbon Credits from them.