Much Better Solar Photovoltaics On the Way

Startup Enphase Energy of Petaluma, CA, is now making its first micro-inverters.  The small inverters can be bolted to the racking under each of an installation’s solar panel to convert DC power into AC for each panel individually. The company claims that the devices will increase a PV system’s efficiency by 5 to 25 percent and decrease the cost of solar power.

Enphase has already teamed with various distributors and partners, including solar module manufacturer Suntech Power Holdings and installer Akeena Solar, to bring its device to customers.  The micro-inverters can be used on residential, commercial, or even utility-scale photovoltaic systems.

There’s much more to solar power than black glassy panels glistening on rooftops.  Perhaps more important now that installations and real world testing is well underway and understood is the inverter performance that convert DC power created by the solar panels into grid-ready AC power.

Currently all the panels in a rooftop photovoltaic system are connected to one large inverter mounted on the side of a house from which the AC power is off loaded to the house or grid.  This is being done as solar panels are wired together in series, and their combined high-voltage DC power is fed to the inverter. From that current flow the inverter’s logic circuit optimizes the total current and voltage levels. But if one panel’s current drops, it becomes the limit of the overall output of the system.

SolarPanel Microinverter by Enphase
SolarPanel Microinverter
by Enphase

Leesa Lee, director of marketing at Enphase points out the problem, “Something as simple as a leaf blowing over a module, or dust or debris or shade on one module, will affect the entire array of all those modules that are connected in series.”  Think bird poop and all the other things falling out of the sky as major problems, but mostly canceling the equality of each panel, that forces production to the least efficient module.  It’s a bigger problem than many realize.

But Enphase’s micro-inverters individually optimize the voltage-current levels at each panel. That uses the most power from each panel and then adds the panels together, increasing the system’s efficiency. “Any problem on a module is limited to that module alone,” Lee says. In addition, the equipment cost for micro-inverters is about 15 percent less than the cost for a traditional system, she says, because expensive DC components, such as signal combiners and disconnects, can be replaced with off-the-shelf AC parts.

Enphase Micro Inverter Points. Click image for a larger view.
Enphase Micro Inverter Points

The problem has been known for decades so the concept of small inverters has been around for more than a decade, but there have been technical challenges to making practical devices. Enphase’s Senior Director for Systems, Mary Dargatz says,  “One of the biggest stumbling blocks to micro-inverter technologies in the past has been conversion efficiency.” So, Enphase has converted many analog parts in the circuits to digital to make the inverter smaller without sacrificing efficiency. The conversion efficiency of an individual micro-inverter is 95.5 percent, on par with efficiencies of traditional large inverters, which range from 94 to 96 percent.

Seems odd, doesn’t it?  The most costly part of a system is hooked up in a 40 year old design that cuts down on the output.  It’s a habit from the 1960s when inverters were very expensive.  Now with micro-inverters on can add to a system without making the inverter, the second most expensive part obsolete. It may be that the micro inverters can be used to upgrade older systems as well.  Enphase offers a long list of downloads to assist owners and installers with analyzing and assessing how the new micro inverter can be used. Its well worth looking over.

Going partway in an attempt to address a broader voltage range, National Semiconductor is making a power-optimizing module for individual panels.  The device only has the logic circuit for optimizing current and voltage levels–it doesn’t do the DC-to-AC power conversion.  What it offers in conversion efficiency looks to be meant for existing installations.

Enphase uses its AC output and ease of connection to offer another service to backup the sale.  The full kit would allow a consumer to send data in for analysis and receive reports via the Internet.  Beyond that, the potential exists for rationing power, if the situation allows, to divide one’s output say for use in the home and for sale.

It all makes for a much more practical implementation of solar arrays with photovoltaic collector panels.  A drop in panel costs, now a drop in inverter cost and a simpler installation should help get home and small commercial arrays more deeply down into the economy where more people can afford the investment.  That more mass market, which should reduce prices as well.

Which brings us to what might be the most important advantage of all.  With the Enphase micro-inverter one can start small and add modules or panels as the budget (or incentives) allow.  Now that’s a path to help build more market, too.  Growth looks good for photovoltaic.

Here is the original post: New Energy and Fuel

Microchip X10 Technical Specs PIC16F877A

X-10 is a communication protocol designed for sending signals over 120 VAC wiring. X-10 uses 120 kHz bursts timed with the power line zero-crossings to represent digital information. Plug-in modules available from various vendors enable users to create home automation systems by using the AC wiring already installed within a home.

Readers who would like an overview of the X-10 signal format may refer to Appendix A. PICmicro® microcontrollers can easily be used in conjunction with X-10 technology to create home automation applications.

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Microchip X10 Technical Specs PIC16F877A

The specific PICmicro microcontroller (MCU) used should be selected based on RAM, ROM, operating frequency, peripheral, and cost requirements of the particular application. The PIC16F877A was selected for this application because of its versatility as a general purpose microcontroller, its FLASH program memory (for ease of development), data EEPROM, and ample I/O.

This application note discusses the implementation of X-10 on a PICmicro MCU to create a home controller that can both send and receive X-10 signals. The reader may implement the home controller as is, or adapt the circuits and firmware to other applications.

A library of X-10 functions is provided to facilitate development of other X-10 applications using PICmicro MCUs (see Appendix E). Operating instructions for the home controller are included in Appendix B.

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New From Elk: 5-Stage In-Line Telephone Surge Protector

The ELK-952 provides exceptional protection against damage from lightning, voltage spikes, and surge damage coming into a phone line. It installs between the RJ31X Phone Jack and the Security Control. The ELK-952 features multi-stage protection and is 5 times faster than MOVs.

It is recommended that the customer install an AC surge arrester in the AC outlet to which this device is connected. This is to avoid damaging the equipment caused by local lightning strikes and other electrical surges.

Source: Home Controls

Don’t Get Hosed And Get The Wrong Hose (or Inlet)

I like central vacuum cleaners. Having the power head in the garage and a series of inlets throughout the house all connected by tubing hidden in the walls is the equivalent of having structured wiring for your telephone, data, and CATV needs.  What I want to bring to your attention, whether you are planning a new install, adding a new inlet, or just replacing the hose, is that you need to make sure that the hose matches the inlet.

All inlets have two, spring-loaded metallic nubs that make contact with a ring on all hoses when the hose is inserted in to the inlet.  This low-voltage contact triggers the power head motor to turn on when the hose is inserted and off when the hose is removed.  The Nutone NU360 is a standard, low-voltage inlet. 

In additon to the low-voltage contacts, there is another type of inlet that has a trapezoidal shaped connector above the circular inlet that allows 120 VAC, household electrical current to safely flow through the hose and drive power brushes and other AC-powered cleaning accessories attached to the hose. The NUCI390 is an example of an electrified, direct-connect inlet.

So which hose do you use? If you have the standard, low-voltage inlet, then the NUCH230 is the hose for you. If however, you needed more cleaning oomph in the form of an electric power brush, you would need to get a different hose such as the NUCH520. The ‘520, pictured above,  can be inserted in a standard inlet, and comes with a six-foot, pigtail AC power cord attached to the inlet side of the hose.  The pigtail allows connection to a nearby electrical outlet thus allowing the use of the power brush.

The third and final hose is the NUCH620.  This is an electrified, direct-connect hose. No pigtail. Just plug it in and you’ve got both suction and AC power at your control.

Original post created by: Home Controls