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How to Grid Tie

Page history last edited by Tom Price 7 years, 1 month ago

return to Practical Engineering

 

 

Grid-tie for the 20kW Power Pallet

 

 

 

We’ve long wanted to provide a reasonably priced grid-tie solution for the Power Pallet. However sync equipment for small scale systems is scarce, and usually at price points near equal the Power Pallet itself.

 

Today we’re announcing the availability of a fully complete, non-hacked, and equipment certified grid-tie solution for the 20kw Power Pallet for $4,995. This is a solution that will work for nearly all global grid standards, as well as enable off-grid parallel feeding with large gensets already at your facility.

 

We think this tie solution is a game changer for the broad usability of the Power Pallet. For years many of you have told us the Power Pallet won’t be relevant for your location until it will connect either to the main grid, or an already existing local diesel grid at your site. Now we can do both. Hopefully this news is as pleasurable for you, as it is for us.

 

The road to here has explored many grid-tie options, and found most all of them less than ideal. Here’s the handicapping of the main scenarios:

  1. An inverter based grid tie, using solar or wind equipment, is in principle easy, but for a 20kw system the inverter alone is @$10,000. You still need to rectify the AC to DC, and more importantly you still need to smart control the genset governor to set power levels and error driven engine shut downs. Also, the combination of inverter and rectifier is going to consume about 10-12% of your power. OK, you can use a PM DC genhead, if you can find one (and ouch on the price) but you still have 5-8% inverter losses.
  2. A synchronous (inductive) genhead is easy to sync as a DIY option, as the grid is energizing the fields, thus sync is native. However, proper async genheads are double the cost of standard genheads, and you still need to add all the genset power controls and protective features. This equipment is mostly only built for large scale systems, and at related price points. Also, asynchronous genheads are usually about 3-5% less efficient than synch ones, and moreso if you are repurposing an inductive motor as a generator.
  3. A sync system for a standard synchronous (auto-exciting) genhead is the typical path, and most efficient path, for grid tie of spinning generating media. However most equipment is made for industrial or utility scale systems, and priced accordingly. To date there been little driver to make this equipment value optimized for the under 100kw market, like there has been for residential scale solar. Furthermore, the equipment has historically been offered as separate control boxes for the different functions: sync control, voltage control, governor control for power level set, and protective functions. When putting all these pieces together I’ve always ended up with prices in the $15-20k range.

What has changed recently on our end recently, is finding new all function integrated genset controller and sync systems that are reasonably priced. In our new world of “electronics always tend towards free”, what was previously complicated multi box systems, are now getting packaged into simple multi function blocks, with nice software and push button interfaces. And certified out of the box!

 

Multiple providers now have interesting options in this space. We reviewed the offerings from Deif, ComAp, Deep Sea, Gov Corp of America, Besler, Woodward, Beckwith, Minco, Heinzmann, etc etc and found the best balance of factors in the Deep Sea Equipment. We chose Deep Sea as it provided not only the most attractive solution for the current grid tie issue, but also has a full line of expansion equipment for future needs like remote monitoring and multiple unit paralleling.

 

Our solution is based on the Deep Sea Electronics 8610 module. We’ve mounted this unit in a custom genhead dog house, and added the needed smart mains contactor, current sensor coils, and interface with our Woodward governor and Power Pallet PCU controls. Sadly the solution is not as simple as just an add-on box to the mains out, as you need to control the genset governor, voltage regulator, and integrate start up and error shut down states across the gasifier and engine control systems. This means a full integration down into the bowels of the Power Pallet control system.

 

Nonetheless, the outcome we’ve achieved is a full and complete onboard solution. This includes gen-to-grid sync, grid feed level control, gen-to-grid voltage matching, grid and gen protective functions, and onboard master contactor for connect and disconnect. All that is left is to run wire from the onboard Power Pallet contactor to your breaker panel on site.  

 

A critical feature of this solution is the elimination of the usual engineering project for the smart mains contactor on the install end. This can be a non-trivial problem, usually found as an after thought in the project. Most grid tie gensets leave this to the installer, which not only requires a smart contactor, but also lots of control wire and current sensors run back and forth between the panel and the generating equipment. Each installation is custom, so an electrical engineer and drawings will be required, in addition to the equipment and install costs. In the process the local code agent is sure to get shaky as they’ve never seen anything like what you’re doing. This problem consumed 10s of thousands of dollars in the 100kW Powertainer project at University of Minnesota, and we still don’t have it correct. Thus here we’ve been highly motivated to solve it all on-board, and relieve you of similar messes in the future.

 

The Deep Sea unit and other added electronics are certified for all common regulatory regimes (most importantly CE). The Mecc Alte genhead is similarly certified. However, the Power Pallet itself is yet to be certified (we’re working on this), but to date we’ve typical found exemptions for experimental or emerging equipment. You need to assess what is likely OK / not OK in your particular location. So far, creativity is working for early and one off installs.

 

Write to “sales@allpowerlabs.org” if you’d like more information.

 

More pictures are at: http://www.gekgasifier.com/products/gallery/new-electronics-and-grid-tie

 

 

Comments (1)

seachanged said

at 10:59 am on Jan 12, 2010

Here's a nice, fully baked article to read about induction generators: http://findarticles.com/p/articles/mi_qa3726/is_200010/ai_n8909370/

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