This project is underway and this page is being used as a tool by the working parties to share and save information. Please excuse any errors or unprofessionalism of the page until it is finished in July.
Background
In 2011, a group of Humboldt State University students went to the Dominican Republic and joined with Dominican Students and La Yuca, a small Dominican neighborhood, to start the La Yuca small scale renewable energy project. The objective of this project was to light the classroom that was built. In the summer of 2012, Humboldt State University students returned to the Dominican Republic to continue working on the project.
Objective
The objective of this project is to improve upon the previous summer’s project. We will be storm proofing the wind turbine, and changing some design aspects to make it more efficient. The energy will be used in the community's school.
Location
La Yuca del Naco, Santo Domingo, Dominican Republic
Criteria
After much team discussion, we decided what aspects of our project were most and least important. We will use these criteria to help us make decisions during the design and building process.
Table 1: Criteria
| Criteria | Weight | Description |
|---|---|---|
| Durability | 10 | Durability is the systems ability to withstand the elements and to continue working without needing to be replaced |
| Effectiveness | 10 | Effectiveness is how consistenly the system can deliver energy to the school |
| Safety | 7 | Safety is the ability of the system to not cause danger, risk, or injury |
| R&D Cost | 4 | Research and Developement Cost is how much money our group will spend to test, design, and develope a working system |
| Reconstruction Cost | 7 | Reconstruction cost is how much the system would cost if it was to be rebuilt using our specifications and design |
| Reproducibility | 8 | Reproducibility of the design is defined as the ability to which the design is able to be reproduced and marketed |
| Payback Time | 7 | Payback Time is the amount of time it would take for the system to generate the amount of energy that would cost the same as the system |
| Ease of Maintenance | 10 | Ease of Maintenance is a measure of how simple it is to protect the system from the elements and to repair it if it stops working |
| Aesthetics | 3 | Aesthetics is a measure of how pleasing the system looks |
Literature Review
Gearing
Gear systems use different sized gears to change the torque of a rotating object. Gear systems are used for bikes, cars, robotics, turbines, and a wide range of other objects.
Gear Ratios
A gear ratio is the relationship between two or more gears that are meshed together. Gear ratios are important parts of gearing systems because they make systems more efficient and precise. To find the optimum gear ratio between one more gears, the number of gear teeth must be counted and compared. For example, if you had a set of two gears, one with 96 teeth and another with 16, you would have a 6:1 gear ratio. A gear ratio of 1:6 means that for every one rotation of the larger gear, the smaller gear will rotate six times. When the larger gear rotates, the smaller gear will have to spin faster in order to maintain an identical rotational velocity as the larger gear. [1]
How to Care for Gears
Gear maintenance for a small scale wind turbine is similar to gear maintenance for a bicycle. Gears are usually all made from metal, which may get rusty if they are exposed to moisture. If gears get rusty they may not spin as well and may even lose their functionality. To prevent gear functions from deteriorating, gears can be lubricated. There are numerous ways to lubricate gears with oil or other substances, which can increase their life by seven years.[1]
Climate
Temperature and Rain
In Santo Domingo the temperature is at a fairly constant and averages around 24 degrees Celsius in January and 27 degrees Celsius in July. The monsoon rain season usually lasts from May to November annually. There is usually an annual rate of 53 inches of rain annually.[2]
Wind
Wind speeds in Santo Domingo range between 2.8 and 7m/s, and the average wind power is 24w/m^2. The southern regions of Santo Domingo have the largest wind resource due to ocean winds. During a hurricane the surface winds can get up to 105knots and speeds of 140mph.[3][4]
Hurricanes
The hurricane season for Santo Domingo is from June until November. Hurricanes usually move in the northwest direction from the Atlantic through Santo Domingo along the coast line up to the northern coast. Hurricanes usually hit Santo Domingo from the southeast.[3][5]
Small Generators
Energy Production Variables
The wiring losses through small generators can reach up to 3-5%. Through a battery-based system there is often a 10% loss due to the need for a small trickle charge to maintain a float voltage, but one should never mix battery types. Inverters in small generators have an efficiency of approximately 85% for a battery-based system, and 90% efficiency for a battery-less system. The power density for small generators varies between the wind velocity and its power.[6]
p = density of wind
Not all of the power in wind is usually available for useful work. According to the Betz Limit, the maximum wind power a turbine can extract is 59.3%[6]
Energy Calculations
Annual Energy Output (AEO)
Basic Parts of a Small Wind Electric System
There are several different basic parts to a small wind electric system. These parts include a rotor, a generator to convert mechanical energy to electricity, wiring to transport that electricity, controllers, inverters, and batteries.[7]
Wind Turbine
Most of the wind turbines that are manufactured today are horizontal axis turbines with two or three blades. The blades are usually made of fiberglass because it is a composite material. The amount of power that a turbine can produce is mostly determined by the diameter of the rotor in the system. The frame of the turbine includes a rotor, generator, and the blades that face into the wind.[7]
Tower
Wind speeds are known to increase with elevation, so turbines are usually mounted on towers. The greater the elevation of the turbine, the more power the system can produce. The more small investments to increase the tower height will also yield a very high rate of return of power production. For example, if you were to raise a 10-kW generator from being at 60 feet to a height of 100 feet, will have a 10% increase in the overall system cost but will also produce 29% more power. There are two main types of wind turbine towers: self-supporting, and guyed. Guyed towers are mostly used for home power systems because they are the least expensive. Guyed towers usually consist of pipe or tubing, lattice sections, and supporting wires. Guyed towers are easier to install because the radius must be one-half to three-quarters of the tower height, in which guyed towers require enough space to accommodate them.[7]
Wire Sizing
Conductors
For wind power and battery systems they are usually always incorporate DC circuits and can also often utilize an inverter for AC circuitry. AC and DC wiring systems should never be mixed in conduit, junction boxes, or raceways due to distinct requirements. DC systems are usually at low voltages which requires them to have a much larger wire size than the AC systems. Larger diameter wires are needed to minimize voltage drops.[8]
The polar environment introduces additional challenges in system wiring. Larger cables used for battery connections become incredibly stiff and difficult to work with due to the insulated sheathing. Coarse-stranded wire intended for residential AC-type use exacerbates the difficulty. Pre-assembling as much of the system as possible will reduce field installation woes. However, installing battery cables and runs from the wind power system are often difficult to avoid. If wires are left to exposure to the environment, they must be rated for that exposure, including UV radiation. ?? UV-resistant sheathing is generally marked as such on the outside. If it does not say “UV rated,” it probably is not. Also, include the correct adapters to bring your cables and conduit into junction boxes and enclosures. Every type of conduit, armored cable, or SO cord requires something a bit different.[8]
Grounding
Earth grounding must be done to every metal electrical box or a component enclosure, and bare metal frame. Earth ground must be connected to every metal electrical box or component enclosure, receptacle, and bare metal frame. In most of the world, it is common practice to ground the turbine tower separate from the actual generator ground wire if the balance of the system is located some distance from the tower. This is primarily for lightning protection, not a major concern in most polar environments but a possibility in some areas. Connect all the ground rods with #4 bare copper and special ground-rod clamps. Alternatively, bare 4/0 cable can be used to create a grounding ring around the perimeter of the tower, equidistant between the tower and the guy anchors.[9]
In most remote systems powering scientific research, the wind turbine tower is often not too distant from the balance of the system. As a general rule of thumb, if the tower is within 100 feet of the balance-of-system components, all ground wires should be tied in common and referenced back to the primary earth ground. The grounding wire is never fused or switched.[8]
Color Coding
Color Coding of Wire[10]
| DC Wiring | 120 AC Wiring |
|---|---|
| Red=Positive | Black=Hot |
| Black=Negative | White=Neutral |
| Green or Copper=Ground |
Rust
Rust A big problem that must be addressed is rust occurring on metallic parts. Rust is the result of oxidation of metal when metal components are exposed to moisture in the air. Water acts as an electrolyte while steel gains oxygen molecules in chemical process called a redox reaction. The environment is a necessary component in the corrosion process which acts like an electrolyte when in contact with the metal.[18] This phenomenon can be a huge deterrence to any use of metallic devices over time. Metal exposed in the atmosphere is hard to completely protect from corrosion however there are preventative measures that can be taken to combat deteriorating metallic equipment. Methods in rust prevention include:.[19][20]
- Choose products that are made of non-corrosive metals like stainless steel and aluminum.
- Metal Corrosion can be best controlled by maintaining a dry environment using suitable moisture barriers and drying agents.
- Remove any existing rust from the object before treating the metal to keep more from forming. Apply rust remover or scrub away rust with steel wool.
- Utilize cleaning agents like soaps, solvents, emulsion compounds and chemicals to efficiently get rid of oil, grease, dirt and other unwanted foreign deposits and follow the correct procedures in applying them.
- Make sure that electrical connections are clean.
- Apply primer to the metal with clean paintbrush, (Bardal, 2004)and then apply paint to protect it from corrosion.
- Allow the treatment to dry and apply a second coat if necessary.
- Galvanizing also provides metal corrosion protection. This is the process of giving a thin coating of zinc or steel material by immersing the object in a bath primarily composed of molten zinc. Galvanizing is an efficient way to protect steel because even if the surface is scratched, the zinc still protects the underlying layer.
References
- ↑ 1.0 1.1 <http://www.mmpa.org/Uploaded_Files/93/93934e74-9b35-4566-b5b4-dad8816fed46.pdf>
- ↑ <http://dominicanrepublic-guide.info/weather/>
- ↑ 3.0 3.1 <http://www.nrel.gov/docs/fy02osti/27602.pdf>
- ↑ <http://docs.lib.noaa.gov/rescue/hurricanes/QC9452B485H81967.pdf>
- ↑ <http://www.nhc.noaa.gov/1998georges.html>
- ↑ 6.0 6.1 <http://www.rurdev.usda.gov/or/biz/QuickGuide2SmallWind.pdf>
- ↑ 7.0 7.1 7.2 <http://www.windpoweringamerica.gov/pdfs/small_wind/small_wind_guide.pdf>
- ↑ 8.0 8.1 8.2 <http://www.polarpower.org/static/docs/WindPower05Apr06.pdf>
- ↑ <http://www.polarpower.org/static/docs/WindPower05Apr06.pdf>
- ↑ <http://video.about.com/electrical/Identify-Wire-Color-Coding.htm>