Feb 8, 2014 Energy Talks
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.
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
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
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Feb 6, 2014 Heating
Gas furnaces come in a variety of sizes and can be used for different applications. By and large, the most common gas furnaces use natural gas and utilize electronic ignition. Electronic ignition gas furnaces are slowly replacing the older style standing pilot furnaces where a pilot light remained lit all the time.
Now, with the newer modern electronic ignition, gas furnaces only use gas when there is an actual call for heat. This adds efficiency because with the older standing pilot gas furnace the pilot remained on even in the summer months. While the heat produced by a standing pilot light is negligible, it is still added heat to the system in the summer when the whole purpose in the summer is to remove the heat from the system rather than add heat like a standing pilot would do.
A gas furnace is rated for efficiency by AFUE or Annual Fuel Utilization Efficiency rating. Furnaces installed before the nineties have efficiency ratings down to 60 percent efficient (or less in some cases). The AFUE ratings of gas furnaces is simply the amount of heat delivered by the gas furnace divided by the fuel used to make that heat.
Another way to look at AFUE is to measure the amount of heat lost up the exhaust stack. If the furnace delivers 90 percent of the heat produced into the dwelling then ten percent of the heat produced is lost up the stack. Even the highest AFUE rated furnace is going to lose heat up the stack.
It is nearly impossible to get 100 percent AFUE out of any gas or oil furnace simply because all oil and gas delivered to a furnace has a small amount of moisture in it. Gas typically has a moisture content of 4 to 5 percent. Oil depends on the quality of oil purchased, how many additives used in the oil, and the integrity of the oil tank and piping system. The end result of all this moisture and additives in the fuels effects the AFUE of the furnace and is the reason why no gas or oil furnace can achieve more than 96 percent efficiency.
The original is here: High Performance HVAC
Jan 15, 2014 Energy Talks
Home Owners Tax Credits
Betcha didn’t know that there was an Energy Policy Act of 2008, did you?
Well, you won’t find any bill based on that name. The passage of last week’s appropriately titled “Emergency Economic Stabilization Act of 2008” is almost a new energy bill.
The Senate prepared a nice summary of the energy-related provisions that were stuffed into the bill at the last minute to get something passed that would “RESCUE” the financial markets. In addition to the Residential Existing Homes Tax Incentives as shown below there are several other clean energy technologies included such as wind, solar, energy efficiency, hybrid vehicles, biofuels, and smart grid.
It’s nice that there has been at least one small silver lining to the dark cloud of the very scary financial implosion of the past few months not to mention our present obvious recessionary predicament.
Here is the information on the incentive for existing homes. Check out the links above to learn more about everything that was included in the bill
Section 201. Extension and modification of the credit for energy-efficiency improvements to existing homes (IRC section 25C). Current law provides a 10 percent investment tax credit for purchases of advanced main air circulating fans, natural gas, propane, or oil furnaces or hot water boilers, windows and other qualified energy-efficient property. The credit applies to property placed in service prior to January 1, 2008. The bill extends the credit for one year (through December 31, 2009), and specifies that certain pellet stoves are included as qualified energy-efficient building property.
Post written by: Ameri-Serv
Jan 9, 2014 Sponge
An impressive idea is out in the International Journal of Energy Research from the University of Leeds and the Chinese Academy of Sciences. The research group has invented a new way to answer quick peak electricity demands.
Peak demand and particularly quick and short-lived peaks are when demand for electricity soars, causing a problem for electric grid operators. The amount of electricity drawn from national grids varies enormously at different times of day. It usually peaks in the early evening for a couple of hours after homes are occupied from people leaving school and work. But it’s the short duration peaks that cause such concern. Those common spikes turn up after major televised sporting events, during commercial breaks and in the morning hours. It’s ‘the everyone hits the microwave and refrigerator’ and those industrial startups with homemakers staring the clothes dryer moments that pull down the available volts and amps.
Grid operators matching the highs and lows in demand with a steady supply is a major challenge. The companies typically top up a ‘base’ supply of energy with electricity from power plants that are just switched on to cope with the peaks. But those natural gas-fired generators often used to feed these peaks are notoriously inefficient, expensive to run and sit idle for long periods of time. The system as it works now is both energy consumption dense and financially consumes lots of money for very little operating time. Answering peaks is a huge chunk of your power bill.
University of Leeds Professor of Engineering, Yulong Ding, and colleagues are proposing a more environmentally friendly system that could also be much cheaper to run.
Of crucial significance, the system would store excess energy made by a plant supplying the ‘base’ demand and use this to supply the ‘peaks’ in demand – as and when they happen. The clever boffins of the UK and China have a fascinating take on forming a fuel to store energy.
The practice is to use excess electricity to run a unit producing liquid nitrogen and oxygen – or ‘cryogen’ from right out of the atmosphere. At times of peak demand, the nitrogen would be reheated to a boil – using waste heat from the power plant heat and as needed from the environment. Step one: the hot nitrogen gas would then be used to drive a turbine or engine, generating the peak demand’s ‘top up’ electricity.
Step two: the oxygen would be fed to a combustor to mix with the natural gas before it is burned. Burning natural gas in pure oxygen, rather than air, makes the combustion process more efficient and produces almost no nitrogen oxide. Instead, the ‘oxygen + fuel’ combustion method produces a concentrated stream of carbon dioxide that can be removed easily in solid form as dry ice. Clean, neat and the only effluent would be what’re produced when making the cryogen. Smartly managed with adequate storage, the efficiency could be quite high.
Operating an integrated system with cryogen and the down process methods the amount of fuel needed to answer peak demand could be cut by as much as 50%. Greenhouse gas emissions would be lower too, thanks to the greatly reduced nitrogen oxide emissions and the capture of carbon dioxide gas in solid form for sale. The base production efficiency if effluent free would make peak demand effluent free as well. It’s an elegant, innovative and simple design that begs the question how could this not have been thought of before?
Professor Ding said, “This is a much better way of dealing with these peaks in demand for electricity. Greenhouse gas emissions would also be cut considerably because the carbon dioxide generated in the gas-fired turbine would be captured in solid form. On paper, the efficiency savings are considerable. We now need to test the system in practice.”
Technically speaking the new system combines a direct open nitrogen (cryogen) expansion cycle with a natural gas-fuelled closed Brayton cycle and the CO2 produced in the system is captured in the form of dry ice. Thermodynamic analyses were carried out on the system under the baseline conditions of 1 kg s−1 natural gas, a combustor operating pressure of 8 bars and a cryogen topping pressure of 100 bars. The results show that the energy efficiency of the proposed system is as high as 64% under the baseline conditions, whereas the corresponding electricity storage efficiency is about 54%, an 10% gain or nearly a 20% improvement.
A sensitivity analysis has also been carried out on the main operating conditions. The results indicate that the baseline performance can be enhanced by increasing the gas turbine inlet temperature, decreasing the approach temperature of the heat exchange processes, operating the combustor at an optimal pressure of ~7 bars and operating the cryogen topping pressure at ~90 bars. Further enhancement can be achieved by increasing the isentropic efficiency of the gas turbine and the liquefaction process. The results of this work also suggest that the power capacity installation of peak-load units and fuel consumption could be reduced by as much as 50% by using the newly proposed system. Further work is suggested for an economic analysis of the system.
The engineering choices for a working design are a huge list with lots of variables to work through for different situations. The outstanding point is the existing generating capacity could fuel up for the peaks leaving the whole investment for fresh fuel sourced peak demand generation out of the cost equation. It’s a superb idea with lots of potential, not just for power plants either.
Here is the original post: New Energy and Fuel