Damien Daly
Small Scale Power Generation in County Monaghan
Abstract
This report is to be a study of possible household small scale energy generation techniques to be used in a specific location in County Monaghan, Ireland
I will look at the energy usage throughout a regular day, and then at energy usage per month throughout the year. These graphs are to indicate my own typical energy usage and will only give a rough idea of the energy usage trends of a typical household.
I will also look at the amount of energy potentially available throughout the year for Hydro Power Generator in a stream on the property, a Wind Power Turbine with local wind trends factored in, and Solar Photovoltaic Panels based on the Mean Global Radiation for the area.
I will compare these technologies to each other, compare the generated energy to the usage, and project how long each system would take to pay for itself and savings gained.
Introduction
"As individuals we are all consumers of energy". We depend on the ability of flicking a switch to do large to small scales of work.
Just about every facet of our everyday social, work and private lives needs energy to make it possible. [1]
This Energy comes in 2 distinct packages,
Depletable
Oil
Gas
Coal
Peat
Renewable
Hydro
Wind
Solar
Tidal
Wave
Bio
Geo-thermal
Nuclear
The first group of energies are fossil fuels, have high CO2 emissions and are seen as one of the major factors influencing climate change. Climate change is seen as such a huge concern globally because an increase in global temperatures could possibly lead to higher sea levels and hence the inundating of low-lying areas. It is also predicted that such an increase could lead to an increased frequency of climatic extremes.
The second group of energies, are "clean" energies and are readily available and are all low or zero-carbon emitting energy sources.
Another problem of the reliance on fossil fuels is that with the huge demand for energy, these resources cannot be economically sustainable
[2]
In general only about 7.3% of the energy produced is supplied by the renewable sector. Of this 18% is supplied by wind farms and other small scale technologies. When comparing this to the benefits that renewable technologies have, it is still a hugely untapped resource.
Energy Usage
Table1 below is typical of a normal daily routine. Breakfast in the morning, absent from the house during midday and afternoon, dinner in the evening and entertainment at night. I used this model to generate an approximate trend graph (Graph1) of my energy usage throughout the day.
(Graph1)
I then used this daily schedule, added average usage of energy per month for heating, and other typical monthly chores to build a yearly approximation of my energy usage. This should give a rough estimation of Energy Usage throughout the year (Graph2).
(Graph2)
Best Case Energy Production
Hydro
[3]
At present Large Scale hydro power is a major contributor to world energy supplies. However it can also be used in small scale state to generate power in streams and rivers in isolated places.
How it works:
1. Flow of Water
2. Water rotates a turbine/propeller
3. Turbine rotates stator
4. Rotating stator induces a current in the field coil resulting in electrical output
Disadvantages:
Can cause flooding
Can upset the ecological system and cause damage to local flora & fauna
Advantages:
No CO2 emissions
No particles or chemical compounds directly harmful to human/animal health
Continuous Generation
One of the most efficient types of renewable energy
Equations:
[4]
Power
P = 10*n*Q*H
where,
P = Power (kW)
n = Efficiency = [coefficient, 1 if 100% - generally about 0.9]
Q = Flow-rate (m3/s) = [cubic metres of water per second]
H = Head (m) = [height in metres through which the water falls]
Flow-rate
Q = V*A
where
A = Average Cross-sectional area (m)
V = Velocity (m/s)
Graphs:
Graph3 shows the difference between Potential Energy Available and Power Generated. Hydro Power if a fairly efficient process. The reason for the difference in the two is partially to the river condition river condition (sediment accumulation), and partially to the efficiency of the generator itself.
[5]
(Graph3)
_________________________________________________
Wind
Wind Energy has been harnessed for at least 3000 years, using windmill to pump water, or grind grain. Its first use to generate electricity can be traced to a 12kW direct current windmill generator by Charles Brush in the late 19th century. Currently there is a growing trend toward large "wind farms" which generate large scale electricity for the countrywide grid. Smaller localised wind turbines are also used to supply some energy needs to building and are generally also connected to the grid. [7]
How it Works:
1. Air passes through propeller
2. Propeller rotates
3. This spins Generator
4. Results in electrical output
Disadvantages:
Intermittent [times of high wind, and no wind]
Needs either storage facilities, or device to change it to workable voltage if being connected to the grid.
Often best locations are remote [no local need for power, no transferring networks close]
Can have loud noise from the blades
Aesthetically unpleasing
Advantages:
No Pollution
Is widely and freely available
Can be used in remote areas [if need for power, but no transferring networks]
Generally the lowest set-up costs
Equations:
[9]
Power
P = 0.5*Cp*p*A*V^3
where,
P = Power (Watt)
Cp = Power Coefficient = [max = 0.593 due to Betz Limit]
p = Air density (kg/m3) = [1.25kg/m3]
A = Rotor Swept Area (m2)
V = Wind Speed (m/s)
Graphs:
The following calculations are for a turbine with a 2metre diameter rotor.
Graph4 below show the difference between a constant low speed wind flow and a burst of high wind speed. Because, power generated is a product of the speed cubed, the turbine would be much more efficient in an area of high intermittent winds, than in an area of constant wind. The chart shows the Energy production per month for a turbine working at the Betz Limit.
[8]
(Graph4)
Graph5 shows the difference between Best Case and Most Likely Energy Generation. Wind Power is limited by the Betz Limit which states that "the maximum fraction of the power in the wind that can theoretically be extracted is 16/27 (59.3%). This occurs when the undisturbed wind velocity is reduced by one-third, when the axial interference factor, is equal to one-third". Most commercial turbines work within the 35% efficiency range.
(Graph5)
_________________________________________________
Solar
"The Photovoltaic effect is defined as the generation of an electromotive force as a result of the absorption of ionizing radiation" It is the direct conversion of light into electrical energy. This photovoltaic effect can be seen in almost any junction of materials that have different electrical characteristics, but the best performance has been seen from cells using semiconductor materials. [8]
How it Works: [taking crystalline silicon cells as example]
[10]
1. A solar cell is exposed to light
2. Photons are absorbed by electrons
3. This energy input breaks electron bonds
4. The released electrons are pulled through the electrical field into the n-region
5. The holes formed migrate in the opposite direction into the p-region
6. The diffusion of charge carriers to the electrical contacts causes a voltage to be present at the solar cell
7. When unloaded, the open circuit voltage arises at the solar cell
8. If the electrical circuit is closed, a current flows
Disadvantages:
Needs either battery storage or connection to the grid
Generally most energy produced is at a time least energy is needed
For best generation panel needs to be south facing an angle of between 30 and 60 degrees, and no shade
Can only change at best about 15% of sun's radiation into electrical energy
Needs big expensive panels
Advantages:
No Pollution
Has huge potential and is freely available
Little maintenance after initial installation
Not dependant on temperature
Equations:
Power
P = [Mean Radiation/m^2]*[kWp of the Panel]
Radiation
1Joule/cm^2 = 0.00278kW/m^2
Graphs:
Graph6 shows the difference between Best Case and Most Likely trend for a 10m^2, 1.5kWp Solar Panel. The difference in the two is due to electron drops in the cell which happen outside of the lab environment,and also due to Temperature Variants and Light intensity difference.
[11]
(Graph6)
Graph7 below shows how much of the Actual Potential Energy Available is transformed to Electrical Energy by the cell, which is generally around 15%.
(Graph7)
_________________________________________________
Combination Results
The following data was calculated using the formula's above and relating information from 30 year means that have been collected and displayed online for the locality of Clones, Co Monaghan.
[12]
Graph8 seen below show's a comparative of each Renewable Source if 100% of the available potential was used for a 10m^2 solar panel, a wind turbine with a two meter rotor, and for a hydro pump in a 1.6*0.25 river with a head of 0.5m and a flow rate of approx 0.13m/s.
(Graph8)
Graph9 show's a more realistic plot assuming that the solar panel is 15% efficient, the hydro-generator is 75% efficient and the wind turbine is 35% efficient.
(Graph9)
Usage Vs Production Comparison
For the purpose of this Comparison I have set the price per unit at €0.13, for both Use and Generation so that the results are more apparent. A household will normally buy its energy for about €0.05 more that it will sell it. [13]
(Graph10)
Difference between use & production
(Graph11)
Return on Investment
Hydro - approx €6000 installed [14]
Wind - 2m diameter rotor, 1kW wind turbine approx €5250 [15]
Solar - 20m^2 solar PV panel approx €12,000 to install [16]
(Graph12)
Result
In conclusion; Hydro-generation would be the most cost effective process for supplying energy to the site. The fact that it has a year round generation and definite measurable values means that it could potentially supply most of the buildings energy needs.
Although the Wind Turbine is potentially a viable cost reduction tool, its unreliability means that at best it can be used only as a savings option.
Although it has the highest potential energy resource, Solar PV is not efficient enough to be an economically viable. Its high cost to install means that little benefit would be seen in its lifetime.
References
[1] Godfrey Boyle, Renewable Energy, 8-9
[2] http://www.whatsupwiththat.com
[3] Godfrey Boyle, Renewable Energy, 177-179
[4] Godfrey Boyle, Renewable Energy, 156
[5] http://www.microhydropower.com
[6] Wiley, Wind Energy Handbook, Second Edition, 4
[7] http://www.windpowersavings.com
[8] Wagner-Mathur, Introduction to Wind Energy Systems, 50
[9] William C. Dickinson, Solar Energy Technology Handbook, 483
[10] Planning & Installing Photovoltaic Systems, Second Edition, 20
[11] http://www.customsolarandleisure.com
[12] http://www.met.ie/climate-Ireland/sunshine.asp
[13] Personal ESB Bill
[14] http://www.nooutage.com/HydroElGen.htm#Hydroelectric Turbine Generators
[15] turbine http://www.jtmpower.ie/samrey-wind-turbine-mistral-1-kw-turbine-grid-tie.html
[16] http://www.my-home-ireland.com/electricity-from-solar-panels
Other Resources
[17] Edward S. Cassedy, Introduction to Energy, Second Edition
[18] Golding, The Generation of Electricity by Wind Power
[19] http://www.seai.ie
[20] http://www.solarite.eu/products/hydro_turbines.html
[21] http://www.teagasc.ie/ruraldev/docs/factsheets/50_SMALLSCALEHEP.pdf
[22] http://www.micro-hydro-power.com/A-Guide-to-Hydro-Power.htm
[23] http://www.ecy.wa.gov/programs/wq/plants/management/joysmanual/5staffguage.html (finding flow rate)
[24] http://www.windturbines.ie/domestic/specifications.asp
[25] http://www.esb.ie/esbcustomersupply/residential/energy_efficiency/appliance_calculator.jsp
[26] Class Notes