*100, 150, 200 W output not available in all input voltages Installing and Using It
Chip Mauck of Sunweaver Energy Enterprises, the supplier of my PV system, helped me get the pump into the well and wired. We used his "pitless adapter tool" ten feet of one inch threaded black iron pipe with a tee and a pipe handle on top) to drop the pump 60 feet down. This put it 34 feet below the apparent "static" water level, giving about 50 gallon of draw down potential. I removed the pitless adapter's built-in check valve and installed a 1/16 inch drain-back hole in a tee just below it. This keeps the pipe into the barn normally empty. I buried the power wires in an extra piece of poly pipe beside the water line.
We hooked the VI-200 up to the pump and battery, wiring the voltage sense pins -S and +S directly to the -OUT and +OUT respectively. I left the Trim and Gate lines unconnected and used an SPST toggle switch to control the pump. Vicor recommends switching the +IN line, because both output lines float high when the -IN line is interrupted. We mounted the converter and switch in a plastic weatherproof box.
Since there's 20 feet of pipe to fill, it takes about 30 seconds for the water to arrive after switching the pump on. All the above-ground pipes sloped so no pockets of water stay behind to freeze, and everything has worked fine through a number of sub-zero nights. Flow rate is a little less than two gpm.
As usual, 20-20 hindsight turns up some things I'd change if I were doing it again: First, if the converter runs hot this summer I'll need better heat sinking. I'd do this by replacing the plastic box with a metal one and using thermal heat-sink grease (available from Radio Shack and elsewhere). Second, I should have gotten a unit with screw terminals and avoided soldering — this is Vicor's "BusMod" packaging option, specified by adding "B1" to the part number. Third, since the SHURflo pump can take up to 30 V, I wish I'd ordered a 28 V output.
Other possible applications that come to mind are: Using 5 V or 9 V gadgets that normally use an ac power cube in a DC-only environment; Replacing one or more inefficient 5, 9, or 12 VDC power cubes with a single central supply; Using power from an EV's main battery pack for lights and accessories instead of lugging and charging an auxiliary battery.
People using Vicor VI-200 series converters in climate-controlled locations could save up to $80 by specifying a narrower operating temperature range. You probably want to specify the wider input voltage range (W or N instead of 1 or 3) if you've got an alkaline battery pack.
Author: James B. Van Bokkelen, Far Acres Farm, 45 Hilldale Ave., South Hampton, NH 03827
Vicor, 23 Frontage Rd., Andover, MA 01810 • 508-470-2900 (Express order line 1-800-735-6200). Computer Products, 7 Elkins St., South Boston, MA 02127 • voice 617-464-6600 • FAX 617-464-6612
Power General, 152 Will Drive, POB 189, Canton, MA 02121 • voice 617-828-6216 • FAX 617-828-5060 or 3215 Pump Manufacturer/Distributor: Windy Dankoff, Photovoltaic Systems Specialist, POB 548, Santa Cruz, NM 87567 • 505351-2100
PV Dealer/Installer: Sunweaver Energy Enterprises, Rt. 4, Northwood, NH 03261 • 603-942-5863
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Mail Order Shoes
©1994 Richard Perez
Ever have to buy your shoes via a mail order catalog? I did when I was younger and overseas with my Air Force family. The only thing wrong with these mail order shoes were that they never quite fit right. They were well made, but painfully unsuited for my feet. If they hurt badly I could send them back. If they only pinched a little, then I'd grin and get used it. Buying a renewable energy system is much like buying mail order shoes.
The most important element in a renewable energy system is the user. Many RE systems are designed, sold and installed with little or no consideration for the system's users. Everyone focuses on the hardware, not the human needs that the system should satisfy. It's time for RE users to demand their rightful place at the center of the system's design. We don't have to be satisfied with "home power system #6" from a catalog. We don't have to buy our system from a dealer or installer who hasn't designed our needs into the
system from the very beginning. It is easy to calculate the rated performance and cost of a pile of hardware. Determining if this hardware is right for the system's users is entirely another matter. A well designed system supplies the user's energy needs from the locally available natural energy sources.
Some folks choose RE because the electric power grid is located at an unaffordable distance. Some folks choose RE because it provides sustainable energy without pollution. Some folks refuse commercial power and go with the security of their own RE system. While the stated reasons for adopting RE are as different as the people using the systems, we all have one thing in common — a need for energy.
Our energy needs have three distinct requirements which the system must satisfy.
1. a list of appliances
2. a reliability requirement
These three requirements are determined by the humans using the system, not by hardware, technology, or even by natural forces. This article is about assessing these human requirements. You will find no equations summing things up here, but a softer, more human look at RE systems
Every home or business has a specific list of energy consumers — appliances. Every system design begins with an accurate and thorough analysis of the loads. Each appliance has its own characteristics — power type (12 or 24 VDC or 120 vac), amount of power required (watts), and duration of appliance use (time). From these characteristics the designer can accurately estimate of the energy requirements of each appliance. The total energy consumption can be easily calculated by summing up the requirements of all the appliances. See page 7 of this issue for a sample load table.
The system's load table shows where inefficient appliances are being used. During the sixteen years that I installed systems, I rarely designed the hardware portion of the system before revising the load table at least three times. The load table is extremely important. Glossing over inefficient appliances or inefficient appliance usage, causes either a needlessly expensive system, or eventual power outages and their associated disappointments.
Every dollar spent on efficient appliances will save three dollars in system hardware. If you are designing your own system, then spend the time and effort to do a thorough load analysis. If you are having your system professionally designed and installed, then giving your system's designer misinformation is akin to lying to your doctor or lawyer. By way of a small tip to system designers everywhere, everyone underestimates the amount of time that they spend watching the TV
Part-time, Full-time, or Overtime
Each of us demands a different type of service from our renewable energy system. For example, the system for a weekend cabin has radically different requirements than a system which powers a home or business. What it really comes down to is what type of duty cycle the user requires from the system.
Consider part-time usage like a weekend cabin. Here the system is in use for two or three days with at least four or five days to recover between use periods. The occasional usage demands of the cabin's user allow for a smaller and less elaborate system. Energy only needs to be stored for a couple of days. The energy source has several days to refill the storage before the system is required to once again deliver power. Parttime systems are easily designed and installed by firsttime RE users.
A home is always occupied; the system must provide power every day. The full-time system's energy storage capabilities must be greater than part-time systems. The full-time system must recover from cloudy or windless periods more quickly than the part-time use system. Full-time systems require design work by an experienced person. But even a full-time home is flexible in its energy demands. For example, if the batteries are depleted, we can put off running the washing machine until a sunny day. Strategic energy use can really stretch a home power system's abilities.
Some systems power businesses or essential services that don't have the luxury of putting off work until the sun shines or the wind blows. I call these overtime systems. For example, the RE systems which power mountain top communications equipment cannot tolerate even momentary power outages. Another less demanding example is Home Power Magazine. All of our computers, scanners, and printers are powered by renewable energy. We have magazine deadlines and simply cannot put work off until the sun comes out. Overtime systems are designed to deliver continuous power regardless of natural energy fluctuations. Here the renewable energy sources are oversized in order to provide almost immediate recovery from extended cloudy or windless periods. Overtime systems usually have at least two energy sources and extended energy storage. Overtime system design is work for an accomplished expert.
Every time the duty cycle of the system increases, so does its design complexity, size, and cost. A full-time system requires much more hardware and expense than a part-time system. In a full-time system, design flaws that are invisible in a part-time system are apparent within weeks of the system's installation. When the system's duty cycle hits overtime, then even the smallest design defect can interrupt the system's constant flow of power. Overtime systems gain their constancy at high costs. Building a system with near 100% reliability costs many times more than building a system with 98% reliability. We are not talking about component failure here. We are talking about the natural vagaries associated with making power from renewable energy sources like sun, wind, and falling water.
Every system should be designed with user participation in mind. Some folks are willing to operate the system with an eye out for natural power production. Other folks want to treat the system as a virtually limitless source — like they were plugged into a utility.
The best form of user participation is knowing when to use the system's full power and when to decrease power consumption. Even this small degree of user participation pays off because the system can satisfy the user with less hardware and thereby less cost. For example, no battery is 100% efficient. Merely using the power when it is produced by the energy source offers a 10-20% dividend over retrieving the same amount of energy from battery storage. A careful user considers the amount of energy remaining in storage. Even if the energy sources are producing, a discharged battery is an excellent reason to reduce power consumption. Wait until the battery refills, then start using the energy as it is produced. And if the sun is shining and the wind is blowing and the batteries are full, then it's time to make a cake in the toaster oven, or run some clothes
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