homer pv energy independent
TRANSCRIPT
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Santiago Sánchez M. • EnerPro Ltda. ECUADOR • Ministry of Energy and Mines of Ecuador • Universidad San Francisco de Quito
Los Membrillos N4444. Quito. Ecuador EMail: [email protected]
Study program in Germany:
PPRE 2001 2002 Internet: www.enerpro.com.ec
German cooperation partners:
Santa Cruz Gardens: An Environmentally Friendly, PV Energy Independent with Grid Backup, Urban Development Housing in the Galapagos Islands
of Ecuador
ABSTRACT
A group of private investors of Ecuador is constructing an urban housing development in the Galapagos Archipelago of Ecuador, South America a very special and fragile place. Of greater concern is the energy supply to the houses since all the electricity comes from diesel generation. The subdivision comprises 60 lots of around 700 m 2 with the entire infrastructure.
The paper describes the application of solar photovoltaics to service the subdivision and having the grid as a backup to reduce the diesel generation in the island.
Special consideration is given to the application of the feedin tariff regulation for renewable energies and an analysis is made comparing the PV generation costs with the conventional diesel generation in the islands, including externalities.
The reality of energy supply in islands is presented, which could be applicable for similar situations and serves the purpose of demonstrating the benefits of renewable energies as compared to oil polluting conventional solutions.
INTRODUCTION
The Galapagos Islands are an archipelago of some 13 volcanic islands and associated islets and rocks in the Pacific Ocean, crossed by the equator, 965 kilometers west of the coast in South America (0° N 91° W). They were named by the first Spanish conquerors that arrived to the islands and found the giant tortoises that have a shell similar to a horse saddle. The Galapagos Islands belong to the Republic of Ecuador since 1837. They were declared World Heritage in 1978 and internationally recognized as a Biosphere Reserve under the UNESCO Man and the Biosphere Programme in 1984. In 1986, the Galapagos Marine Resources Reserve was established. This was upgraded to a Biological Reserve of Marine Resources in December 1996. The wildlife of the Galapagos Islands has been documented for centuries, first discovered in 1535 and used as a stopping point
Santa Cruz Gardens
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for ships; Charles Darwin also visited the Islands in 1835 and the development of many unique species contributed largely to the theory of evolution.
The Province of Galapagos covers a land area of 7882 km 2 and 45.000 km 2 of sea. Almost 96% of the total area is a national park where no settlements are allowed. Population as of 2006 is around 30.000 people, half of them living in Santa Cruz and its main city of Puerto Ayora.
The Government of Ecuador has given a special attention to preserve this pristine environment and is supporting the installation of renewable energies to reduce the consumption of diesel for electricity generation.
Energy situation in the Galapagos Islands
The local Galapagos Province Power Utility (EEPG), that is responsible for the generation and distribution, serves the four inhabited islands of Santa Cruz, Isabela, San Cristobal and Floreana. Electricity production in 2005 was 22,9 MWh coming from 18 small generation sets that burned 1,86 million gallons of diesel. Total fuel consumption in 2005 was 5,6 million gallons of diesel, and 3,6 million gallons of gasoline. Electricity generation accounts for 33% of total diesel consumption in the islands.
Total effective installed capacity is 7,4 MW, of which 57% is in Santa Cruz, 29% in San Cristobal, 12% in Isabela and 1% in Floreana. As of December 2005 the number of users of EEPG was 6171 with a load increase of 7.5% to 10% depending on the island. This brings out a serious concern to the authorities to provide the needed basic services, including electricity.
Actions from the Government and International Donors
The Ecuadorian authorities headed by the Ministry of Energy and Mines have initiated actions to control the energy situation in the Galapagos and have called for international support. Various organizations are involved in reducing the use of fossil fuel for electricity generation and some agreements are in force with the purpose of substituting the generation with renewable energies.
The National Electricity Board (CONELEC) issued a regulation in 2002 stating a feedin tariff for generation from renewable energies. This was revised in 2005. The prices are:
RENEWABLE ENERGY SOURCE
PRICE (¢USD /kWh) Continental Territory
PRICE (¢USD/kWh) Galapagos Islands
WIND 9.31 12.10 PHOTOVOLTAIC 28.37 31.20 BIOMASS AND BIOGAS 9.04 9.94 GEOTHERMAL 9.17 10.08 SMALL HYDRO UP TO 5 MW 5.80 6.38 SMALL HYDRO 5 TO 10 MW 5.00 5.50
The price of power generation from thermal power plants in the mainland ranges from 0,0334 USD/kWh to 0,1384 USD/kWh. For diesel plans of similar size to the ones of EEPG the average cost is USD 0,1094/kWh.
In the Galapagos the price for generation per island for the year 2005 was:
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The difference is due to installed effective generation capacity and the number of households: Floreana has 77 kW to serve 44 households; Isabela 887 kW for 667 households; San Cristobal 2169 kW for 1994 households; and Santa Cruz 4237 kW for 3421 households.
The real cost of diesel, including the subsidies and transportation from the mainland is around USD 2,0. The price of diesel is USD 1,0 and the difference is covered by a governmental subsidy coming from the National Urban and Rural Electrification Fund.
In spite of the incentives for renewable energy generation in Ecuador, not a single project has come yet into service. This is caused basically by the lack of a national energy policy and the default in payments by the power utilities to the generating companies since the real cost for the distribution sector is ¢USD 10.80/kWh creating a gap that supposedly should be covered by the Government but it has not come into effect and is causing a critical financial situation in the electricity sector of Ecuador.
The ERGAL project of UNDP
Deeply concern was brought up in the year 2001 with the oil spill of the “Jessica” tanker hit the island of San Cristobal. Almost 240.000 gallons of fuel invaded the bay (160.000 of Diesel 2 and 80.000 of bunker fuel). Fortunately the impact could be controlled on time with minor environmental damage. The up to then preliminary initiatives to the introduction of renewable energies by the United Nations Development Program (UNDP) were taken more seriously and an agreement was signed in 2003 between UNDP and the Ecuadorian government. Support from the Global Environmental Facility (GEF) and the United Nations Fund (UNF) was obtained and the Electrification of Galapagos with Renewable Energies project (ERGAL) was established, having the Ministry of Energy and Mines as the implementing agency and committing local financing. The executing agency is the local power utility EEPG.
The ERGAL project comprises the installation of several RE projects in the islands:
ISLAND CAPACITY SOURCE AMOUNT IN MILLIONS/ DONORS STATUS
Floreana 18.5 kW PV mini grid USD 0.8 Spain cooperation In service Isabela 700 kW PV mini grid Santa Cruz 120 kW PV mini grid
€ 7.85 KfW cooperation Germany Studies
San Cristobal 2.4 MW Wind farm
Total USD 10.5 e7 Group USD 5.44 MEM USD 3.2 UNF USD 0.93
Construction. Operation Jan
2007
Santa Cruz 3.2 MW Wind farm
Total USD 8.7 MEM USD 1.5 UNDPGEF USD 3.2 UNF USD 0.65 Pending USD 3.4
Studies
The first result of the ERGAL project is the Floreana project with the putting into service of 18,5 kW from a PV mini grid late in 2004. A sustainability model including prepayment from users is in progress.
Altogether, the projects represent an investment of USD 30 million and will allow the substitution of 1 million gallons of diesel and the reduction of 12000 tons of CO2 per year.
ISLAND USD/kWh San Cristóbal 0,1707 Santa Cruz 0,1128 Isabela 0,2495 Floreana 0,5816
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In addition to the technical aspects of the projects, the ERGAL project also includes social, environmental and political aspects involving information, promotion and awareness to the public of the benefits of renewable energies and energy efficiency. It is not just a matter of replacing fossil fuel generation with clean energies, and keeping the same energy use pattern. Efforts should be supported in parallel to educate the families in using energy more efficiently and changing some consumption patterns copied from the continent were energy can be dispended.
One of the means of showing that the community and the private initiatives have to cooperate to improve the energy use in the Galapagos and the feasibility of renewable energies is the construction of the Santa Cruz Gardens (SCG) housing development project.
SANTA CRUZ GARDENS URBAN DEVELOPMENT
Reference data
The guiding principles of the SCG subdivision go beyond the observance of the rules of the Galapagos National Park but call the owners to understand what makes the islands so special and their help improving understanding of what makes the Galapagos so remarkable and their responsibility to help improving the local economy and their concern on nature.
RESERVE ZONE 61977.64
GALAPAGOS NATIONAL PARK
COMMUNITY ZONE 36244.77
COMMUNITY ZONE 23144.64
PROTECTION ZONE
STREET 3
STREET 2
STREET 1
STREET D
STREET C
STREET B
STREET A
DIFFERENT OWNERS
FROM PTO. AYORA
"TOMAS DE BERLANGA" SCHOOL
35855.74
DIFFERENT OWNERS
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3398.23 7896.27
17510.89
7787.91
7451.12
7906.48
7317.75
7700.08
7676.81
7014.78
7010.70 8121.47
8127.60
8222.31
8520.79
8236.5
8193.28
8009.45
8021.80
8021.39
8013.01
7812.84
7741.33
7710.51
7496.91
7550.66
7653.86
7576.48
7524.54
7663.32
7663.32
7515.94
7565.82
7660.63
7524.80
7783.71
7817.36
7766.41
7684.60
7690.30
7710.72
7579.15
10656.71
8070.30
7863.48
7605.91
7378.66
7928.09
7752.33
7685.03
7728.03
7728.03
7714.49
7709.97
7756.52
7758.73
7728.25
B2
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RESERVE ZONE 61977.64
GALAPAGOS NATIONAL PARK
COMMUNITY ZONE 36244.77
COMMUNITY ZONE 23144.64
PROTECTION ZONE
STREET 3
STREET 2
STREET 1
STREET D
STREET C
STREET B
STREET A
DIFFERENT OWNERS
FROM PTO. AYORA
"TOMAS DE BERLANGA" SCHOOL
35855.74
DIFFERENT OWNERS
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3398.23 7896.27
17510.89
7787.91
7451.12
7906.48
7317.75
7700.08
7676.81
7014.78
7010.70 8121.47
8127.60
8222.31
8520.79
8236.5
8193.28
8009.45
8021.80
8021.39
8013.01
7812.84
7741.33
7710.51
7496.91
7550.66
7653.86
7576.48
7524.54
7663.32
7663.32
7515.94
7565.82
7660.63
7524.80
7783.71
7817.36
7766.41
7684.60
7690.30
7710.72
7579.15
10656.71
8070.30
7863.48
7605.91
7378.66
7928.09
7752.33
7685.03
7728.03
7728.03
7714.49
7709.97
7756.52
7758.73
7728.25
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Figure 1. Subdivision layout and feeders to the houses and communal services
The subdivision comprises 60 lots from 700 to 1000 m 2 . The developer, an Ecuadorian private entrepreneur is responsible of erecting the houses with energy efficiency concepts, including the used of efficient electric appliances. Lot owners have agreed to obey the rules for the subdivision that prohibit the use of automobiles. An electric car shuttle will be offered to transfer to the town of Puerto Ayora away 6 km from SCG on a paved road.
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Energy premise: PV standalone with grid as a back up
The basic premise behind the energy supply in SCG is to reduce as much as possible the use of fossil fuel from the EEPG grid. As such, each house will be energy independent having its own PV standalone installation. The PV system will be grid connected but unlike a typical connection in which the PV system acts as a back up when the grid fails, in SCG, they will supply all the energy required by the load and any excess will be delivered back to the grid.
The system is conceived as a hybrid where the grid covers the load of the communal services (laundry, communal house, street lighting and pumping). In extraordinary events of failure of the PV systems or low battery storage, the grid could provide energy to the houses.
PV SYSTEM DESIGN
The steps to the design of the PV system are: load estimate, battery storage, PV array, inverter and balance of system.
House load demand
Two house plans are offered to the lot owner for construction, one of 120 m 2 (two bedrooms) and the other of 140 m 2 (three bedrooms). The load difference is an extra light fixture and a ventilator for the larger house; to estimate the load this large house was considered.
At first it was analyzed the possibility to serve the lighting load directly with DC and the remaining loads with AC, but it would imply having two load centers and separate feeders. Since the PV system will have an inverter, it was decided that the total load will be served with AC.
The number of fixtures, loads and hourly use for the household is:
1) Load demand AC APPLIANCE W Qty. Hours Wh/day
Compact fluorescent 16 17 3,50 952,00 Spot light 30 14 2,10 882,00 Wall lighting fixture 16 4 4,20 268,80 Refrigerator 90 1 7,68 691,20 TV 35 1 8,40 294,00 Radio 8 1 5,00 40,00 Blender 300 1 0,15 45,00 Ventilator 30 4 4,00 480,00 Stereo 20 1 2,00 40,00 DVD 35 1 1,00 35,00 Laptop PC 35 1 3,00 105,00 Others 25 2 3,00 150,00 Air conditioner window type 1000 5,00 TOTAL Wh/day AC 3.983,0 Load W AC 1.449,0 TOTAL kWh/month AC 95,20
Total daily energy is close to 4 kWh, equivalent to 120 kWh/month. And total load is 1,45 kW. Considering that energy efficient appliances are used, the load represents a typical mid size house in Galapagos.
The daily load curve is shown below. The peaks are in the morning 6H00 to 8H00 and in the evening from 19H00 to 22H00. Is should be noted that being located in the equator (lat. 0º) daylight hours are 12 all year around.
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Temperature ranges in Puerto Ayora (Santa Cruz Gardens) from 15ºC to 32ºC during the year, so there is strictly not a need for air conditioning; instead, ventilators are preferred. An air conditioner
would demand an extra load to be served from the PV system and increase considerably the demand and the size of the PV system.
Having the load demand for each house, the next step is to design the PV system.
To serve the load and the daily energy demand, the voltage of the PV system was set to 48 Vdc. The system will include the PV array with 24 Vdc panels, the battery bank, the inverter, the charge regulator and the protection elements (disconnector, fuses and breakers), and the cabling.
Solar radiation data for the site was obtained from field measurements of 4 years taken by EEPG. Mean global horizontal radiation is 4,76 kWh/m 2 day (sun hours).
The native PV systems in the houses will provide all the energy required by the load and the excess will be sold back to the grid. A consideration was given as to the degree of occupancy of the dwellings since houses are mostly for vacation purposes and owners will most likely not stay the whole year in the islands. This is dealt in the benefit – cost analysis.
A simulation was run using HOMER and the share of electricity production from the grid and from the PV resulted in:
2733 kWh (89%) 355 kWh (11%) Total 3088 kWh
Graph 1. Dai ly load demand curve
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Battery Battery Battery
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Communal services for street lighting, laundry and drying machines, pool pump and four sewage water treatment pumps will be served directly from the grid distribution transformer.
Energy produced from the PV array will charge the batteries to provide through the inverter the required energy. Battery size, then, sets the parameters for the SHS dimensioning.
Calculations to determine the total Ah load follows.
2) Electrical demand in Ah a. Load demand DC+AC Wh/d 3.983,00 b. System voltage DC Vdc 48,00 c. Ampere hours Ah 82,98 d. System degradation % 10% e. Effective ampere hours Ah 92,20 f. Reserve % 10% g. Total Ah load Ah 102,44
The next step is to size the battery bank.
3) Battery bank sizing a. Total load Ah Ah 102,44 b. No sun days (3 to 5) Days 3,0 c. Total Ah needed Ah 307,33 d. Depth of discharge (0.2 to 0.8) DoD 0,50 e. Battery bank capacity Ah 614,66 f. Rated Ah of each battery Ah 200 g. Battery series calculated U 3,07 h. Battery series selected U 3 i. Battery voltage V 12 k. Batteries per serie U 4 l. Total batteries U 12 m. Total Ah in batteries Ah 600
The batteries will be installed in a vented area under the floor, so AGM VRLA type batteries were chosen. This deep cycle battery requires no maintenance, has almost negligible emissions, is safe to dispose and handle, and has no restrictions to be shipped by sea or air. Special consideration was given to keep the state of charge of the batteries, with the results shown below:
The PV array to charge the batteries was then calculated.
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4) PV array a. Total load Ah Ah 102,44 b. Battery efficiency % 90% c. Effective amperes for batteries Ah 113,83 d. Solar radiation kWh/m2/day 4,76 e. Calculated amperes from PV Ah 23,91 f. Maximum panel current Im A 5,53 g. Panel peak power Wp 220,00 h. Panel rated voltage Vdc 24,00 i. Calculated number of panels u 8,65 j. Panels per serie u 2,00 k. Calculated number of series u 4,32 l. Selected number of series u 4,00 m. Total panels u 8,00 n. Total array power Wp 1760,00 o. Array production per day Wh/day 8377,60 p. Array production per month kWh/month 251,33
Several choices where considered for the panels and the Sun Power SPR220 Wp was chosen because it gave the lowest initial cost and reduced the transportation and installation costs.
Due to the high solar irradiation available, PV output reached at times values larger than 1000 W. This has to be considered in the dimensioning of the charge controller and the fuses and disconnecting elements of the PV system.
The next step was to size the charge controller and the inverter, resulting in:
5) Charge controller a. Isc panel A 5,95 b. Panels per series U 2,00 c. Total amperes A 11,90 d. Charge controller rated capacity A 50
6) Inverter a. Total load W 1.449,00 b. Demand factor % 95% c. Total demand W 1.376,55 d. Inverter efficiency % 90% e. Calculated inverter capacity W 1.529,50 f. Rated inverter capacity W 2.500
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The OUTBACK PS12500 gridtie with battery backup model was chosen. This equipment includes the charge regulator with maximum point power tracking (MPPT) for maximum efficiency, the inverter, ground fault protection, low harmonic distortion, AC transfer switch, battery temperature sensor, all nicely packed in a sturdy case rainproof for outdoor installation.
The cables to connect all the elements of the PV system where properly sized for ampacity and voltage drop.
7) Cable sizing Connection Section AWG Section mm 2
a. PV arraycharge controller 2/0 67,43 b. Charge controller – inverter – battery 1/0 53,52 c. Inverter – load center 4 21,15
SUBDIVISION DISTRIBUTION GRID
As mentioned, the houses will have their own energy supply from the PV systems. Owners of the lots are mostly foreigners and probably will not stay in SCG the whole year. When the house is not occupied, the energy from the PV SHS will be delivered back to the grid.
For the design of the distribution grid, the total load of the urban development was considered including houses, lighting and communal services, resulting in:
Demand Santa Cruz Gardens SERVICE LOAD W QTY. DIVERSITY FACTOR TOTAL LOAD W
PV ARRAY Houses 1449,0 60 0,9 78246,0 Feed back to grid from PV 78246,0 1 0,5 39123,0 DELIVERED TO GRID 39123,0 GRID House sidewalk lighting 26,0 120 0,9 2808,0 Street lighting 70,0 50 1,0 3500,0 Communal laundry mat 7500,0 1 0,6 4500,0 Pool 3730,0 1 0,8 2984,0 Communal house 2500,0 1 0,5 1250,0 Water treatment plants 22380,0 1 0,6 13428,0 Other loads 2000,0 2 0,8 3200,0 LOAD FROM GRID 31670,0 DISTRIBUTION TRANSFORMER kW 70,8 Power factor 0,92 TRANSFORMER KVA 76,9
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The load of the communal services amounts to 31.6 kW. The request to EEPG is to install a 75 KVA singlephase three wire 13.200V/120240V distribution transformer at the subdivision property. At present, a 1,5 km singlephase distribution line departs from the main distribution feeder along the road that is 4,5 km away from the city of Puerto Ayora to the island of Baltra.
Total PV installed capacity is 105.6 kW for the 60 houses. It has been estimated that 43 houses will be built in the first five years and occupancy in that period will increase. The total development will be full in a 10year period. With the occupancy and houses built, it was calculated the total PV energy sold to the grid taking an annual production per house of 2733 kWh (89%) from the PV SHS, and a backup from the grid of 355 kWh (11%). Annual primary load served is 2404 kWh. These results are shown below:
YEAR Houses built per year Total kWh Cumulative total kWh Occupancy
PV energy sold to grid
kWh
Cumulative PV energy sold to
grid kWh
1 10 27.330 27.330 50% 13.665 13.665 2 10 27.330 54.660 50% 13.665 27.330 3 8 21.864 76.524 55% 12.025 39.355 4 8 21.864 98.388 55% 12.025 51.380 5 7 19.131 117.519 60% 11.479 62.859 6 6 16.398 133.917 60% 9.839 72.698 7 4 10.932 144.849 65% 7.106 79.804 8 3 8.199 153.048 65% 5.329 85.133 9 2 5.466 158.514 70% 3.826 88.959 10 2 5.466 163.980 70% 3.826 92.785
11 to 20 0 163.980 92.785 SUM 60 2.768.529 1.541.822
Energy delivered to the grid adds up to 1,54 GWH in a 20 year period.
Feeders
Dimensioning of the feeders estimates the total load of houses and communal services under the premise that in the future a large share of the energy supply in SCG will come from renewables and SCG could connect to his source via the existing grid. As offered by the developer, the feeders will run underground.
The soil in Santa Cruz Gardens and in Galapagos is volcanic rock, very difficult to dig. In fact, the streets were built on top of the ground by filling gravel material brought from a near bye mine. To avoid digging in the rock, the idea is to extend 2 meters the road (6 meters wide) to build the sidewalks at a height of 405 cm and install there the ducts and holes for the electrical installations and the water and sewage pipes.
PVC pipe 10 cm of diameter will be used for the electrical underground ducts. On the sidewalk, in the border between two houses a small man hole (40x40x40cm) will allow the
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connection of the houses to the secondary feeders. Together with the main load feeders a separate feeder will serve the street lighting.
Feeder voltage drop calculations
Calculations were made with a voltage drop of 5% at the end of the line. One thing to have in mind when doing the voltage drop calculation is the fact that at the same time and depending on the occupancy of the houses, some PV systems will be delivering energy to the secondary feeders while other houses will be consuming energy. In strict manner, the net flow should be considered for the calculations but since this cannot be predicted before the systems are in operation and the behavior of the house owners is random, the design was dimensioned for the full load. This will allow some reserve capacity to be available for future load increase.
One of the considerations of the PV system for grid connection in Ecuador is the secondary voltage. This is according to USA standards, 120V phaseneutral and 240V phasephase (for a single phase 3 wire system, and 210/121 V for a three phase). In Europe phase to neutral is 220 V. European 50 Hz inverters cannot be used directly in Ecuador because frequency is 60 Hz. For long distribution lines, which is not really the case in SCG, the wire gauge is in direct relationship to the voltage, so a possibility could be to install a stepup transformer to a higher voltage at each house. This will increase the cost of the installation and there is no known experience that this practice has been done before commercially.
Copper or aluminum wire could be used for the secondary feeders. Overhead wires prefer aluminum while underground uses mostly copper. Due to the high increase of price of copper in the last year and to reduce the weight of the cable, since it has to be shipped from the continental Ecuadorian territory, insulated aluminum cable will be used for the feeders.
Main load center
A main distribution load center will be installed at the SCG entrance, next to the transformer. It will include the breakers for the feeders of the different loads. The load of the feeders will be balanced according to the number of houses each will serve. Total houses feeders are 6, plus one for street poles and two for the communal services including the pumps.
PV standalone vs. GRID
Installing PV to cover the total load SCG would demand additional PV arrays for the communal services. This investment will have to come from the owners. In addition, the service voltage for the water sewage treatment pumps is 240 V. To obtain this voltage would require having two PV systems to cover each, half the load and with suitable inverter connection, or to install a transformer to raise the voltage; this could be done more efficiently and at less cost from the grid.
The main advantage of installing SHS in the houses is that the owners will have their own generation, independent from the grid and will deliver any excess back to the grid. In doing that, the owner will be paid a feedin tariff of USD 0,3212 / kWh that will allow covering at least the operation and maintenance, and replacement of parts (including the batteries) during the 20year lifetime of the systems, plus the depreciation costs.
PV SHS VS. PV MINI GRID
For purposes of considering other alternatives to serve the energy requirements at SCG, the possibility of installing a micro grid PV was also taken into account. A micro grid differs from the PV SHS in that the solar array is located in one or two places of the urban development and not at each house. The benefit of the micro grid lies in the fact that not all the houses have the same use of energy so, a larger plant considers this diversity factor to install a smaller system to serve the houses. The main difficulty in the case of SCG is that the houses will not be built on the first
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years and the micro grid would have to be dimensioned from the very beginning for the total development, i.e. the 60 houses. Also, the connection to the grid would have been more difficult due to the need of specialized inverters to handle the singlephase voltage.
There is also the fact of the property of the micro grid and the allocation of benefit of sales to the grid. Some owners with no houses built yet will be required to pay for the micro grid PV making it more difficult the distribution of expenses and earnings. This has to do also with the maintenance costs that are higher than for the individual systems, and it is always the case that some owners do fail to pay on time for the services, putting in jeopardy the whole electricity service.
Finally in the case of the micro grid there is the problem of the voltage level. The feeders are quite large, at some point up to 300 meters so the wire size should be larger also, increasing the costs of the system.
It was decided then to choose the individual PV SHS at each house rather than the micro grid PV alternative.
ECONOMICAL ASPECTS
The cost breakdown of the total PV SHS for SCG is shown below (from HOMER) with description of the initial capital costs, replacement, and operation and maintenance including the administrative costs.
Initial Capital
Annualized Capital
Annualized Replacement Annual O&M
Total Annualized Component
USD USD/p.a. USD/p.a. USD/p.a. USD/p.a. PV Array 12.473 976 67 83 1.125 Grid 0 0 0 41 41 Battery 3.000 235 423 48 588 Converter 2.716 212 72 60 345 Other 300 23 0 120 143 Totals 18.489 1.446 562 351 2.242 Installation and transport 10.892 Totals 29.381
Under the conditions of the designed PV system, the net present cost is USD 30.169 with a levelized cost of energy of USD 0.982 /kWh.
The estimated cost per house for the 1,76 kWp SHS runs around USD 29.400, including the installation and the transport of the equipment to the Galapagos.
All efforts made so far to establish regulations in the energy sector in favor of renewable energies have faced lack of support from authorities, basically because they prefer the conventional solutions with largescale centralized generation plants and are unaware of the benefits of distributed generation. One of the reasons for the success of SCG with renewables is that the developer is a private entrepreneur and the owners are environmentally concerned people willing to show there is a different way to do things.
The cost of the total distribution system per house does not exceed USD 4000; which is the same for grid or PV.
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Altogether, the cost per house of the PV solution plus the distribution feeders is around USD 33400, equivalent to 25% of the total cost of the house.
The PV SHS should be properly operated and maintained and sufficient funds shall be allocated to replace the equipment to assure an effective service during its lifetime. Lifetime for the inverter and batteries are 10 years.
BENEFITCOST ANALYSIS
In order to determine the benefits and costs of the PV SHS solution a simulation was performed. One thing to have in mind is that installing a PV SHS is more a decision of the owner to favor a clean environment. Not all the benefits should necessarily be weighted on a monetary basis. When a house is built it doesn’t come up the question of what is the repayment time for a wooden floor or a fancy kitchen. Why it is then that PV should be compared to the electricity from the grid, just because it gives away free energy? PV, from the time being should be considered as any other expense in a house that in addition brings back savings to the owner, like any other energy efficiency appliance.
The main benefit of installing PV in SCG is the reduction of diesel consumption in the power plants of EEPG. The beneficiary (EEPG) should recognize this and should pay for the generation produced, in accordance to the Reg. 004/04 of CONELEC. The results of the benefit cost ratio analysis for the 20year lifetime of the systems in SCG are summarized below. Al values are constant. In the estimation it was considered the number of houses being built each year. The initial costs were not taken into account. The table shows the fact that the oil spill risk is reduced but no monetary figure could be derived, and also that might be a possibility to apply for a buy down subsidy from the Government for the installation of the systems.
The benefit cost ratio per house in the 20 year period is USD 3.205.
The cost per year per house without depreciation is USD 267,13, which is a low value considering the level of income of the owners of the houses. The results show that applying the feedin tariff, in spite the fact that the PV solution does not really assures a payoff of the investment, it does provide the income to cover the operation and maintenance and replacement of parts during the lifetime.
DESCRIPTION Unit Quantity USD/Unit USD Total BENEFITS
Energy sold to the grid kWh 1.541.822 0,312 481.048 CO2 reduction ton /CO2 294 5,00 1.470 Diesel saved Gallon 122.270 2,00 244.540 Oil spill risk reduction 0,00 O&M diesel plants 0,00 Buy down subsidy 0,00 SUM BENEFITS 727.058
COSTS Grid purchase kWh 200.273 0,089 17.824 O&M PV SHS house 383,00 387.979 Replacement PV SHS house 507,00 513.591 SUM COSTS 919.394
BENEFIT COSTS 192.336 NPV/house 3.205,61 NPV/houseyear 267,13
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OTHER ASPECTS
Benefits of the PV embedded generation at the house's premises can be grouped in the following aspects:
a) Technical
• Reducing energy load from the grid allows availability of power from thermal plants to be delivered where it is required. Not a burden to EEPG.
• Deferral of investments in extending the distribution system. No need for new transformers; less losses.
• Generation at the end of the line allows for better power flow in the existing grid. • A draw back could be the need to install local capacitor banks at the grid transformed
node to compensate for the lack of reactive power from the PV generation. • Less losses in the secondary feeders because net power is less than in a conventional
system. • 120 V at the secondary distribution forces larger wire sizes. • System is prone to natural variability of the solar source. Requires to have a larger
battery backup storage.
b) Environmental
• Significantly reduces the use of fossil fuel from existing diesel generation to power the urban development. Renewable energy fraction during the year is 89%. Total tons of CO2 reduced in the lifetime is estimated to be 294 tons. The years when the 60 houses are built it comes to 17,4 tons of CO2 per year.
• Reduction in diesel consumption for SCG under the consideration of occupancy explained above comes up to 122.270 gallons for the 20 years, averaging 7358 gallons in the years when all houses are built (at 12,61 kWh/gallon).
• Although this amount is rather small considering the total diesel consumption in the islands, this could be replicated in other places to serve the purpose of fuel oil displacement. This solution could also be applied in the mainland where at present there is a large electricity shortage because of the lack of new generation plants.
• Battery disposal has to be carefully planned as not to become a problem. Suggestion is that the supplier should be responsible for the replacement of batteries and sign an agreement for disposal when the purchase is made so that any costs are already accounted for.
c) Social
• Some national and international NGO´s have been working actively in the Galapagos to introduce renewable energies and energy efficiency awareness in schools. The local power utility EEPG has assumed its responsibility in the installations of new generation from renewables and has also started a programme in energy efficiency. As part of this activity a study was performed for the capacity building of EEPG that recommends its restructure to include renewables.
• People are getting more familiar with the renewable energy and energy efficiency issues and are supporting them. Nevertheless, much work is yet to be done to raise awareness as to the use of energy, including the expense of fuel in boats and vehicles.
• SCG can serve as a demonstration project of how things can be done using renewable energies and reducing the fossil fuel use. At a latter stage measures and regulations shall be prepared by authorities to control the use of nonefficient appliances and promote biofuels and electric cars for transportation.
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• Community involvement is a key factor in this concept; so additional funds must be allocated at the local level to continue in the effort to substitute as much as possible the use of fossil fuels for energy purposes. Some work has already been done and there are projects in waste disposal, such as the gathering of used car oil to send it to the main land for treatment. Same thing is done with the oil of the diesel gensets of EEPG.
• Political authorities should also get involved in the solution and pass regulations such as: the use of efficient appliances specially refrigerators and freezers, installation of compact florescent lighting, replacing the electric showers and electric water heaters with solar thermal collectors, and giving guidelines on the construction of energy efficient buildings and houses. These all will have required the support from the national government.
d) Externalities
• The installation of PV SHS as compared to the grid brings out the question of what is the real cost and benefit of the PV solution. Under the special circumstances in the Galapagos, where the nature habitat is priceless, any cost to reduce the impact on nature should be weighted accordingly and takes into account not just the reduction in fuel use but also the externalities involved.
• The costs involved in an eventual risk of an oil spill in the Galapagos should also be weighted. Past experience shows the damage it caused to land and sea life.
• Reducing the green house gas emissions should also be weighted and accounted for in energy calculations, but this is not considered yet for PV installations. The application of the clean development mechanism in PV has not been very extensive yet, but islands should be given some preferred treatment.
TARIFF STRUCTURE OF PV VS. GRID
In the case of SCG it is of interest also to determine what will be the administration costs involved for the supply of electricity from the PV and the grid and what tariff to apply. In a conventional system, EEPG will apply the VAD (distribution value added ratio) that includes all the costs of the power utility to deliver a kWh of energy at the distribution level.
For SCG it is not clear how this will be dealt with. Usually the utility charges the energy consumed and the demand. But according to the regulations this is applicable just for large industrial consumers with a demand greater than 660 kW/month and 4500 MWh per year; by far not the case in SCG. The transformer capacity should not be taken as the value for the demand, but instead consider that a new generation plant of the same size as the transformer is now serving the distribution grid, with no investment from EEPG.
All these issues should be clearly agreed with EEPG and the electricity national authorities because there is no previous experience in embedded generation in Ecuador. The Regulation 004/04 for feedin tariffs is not applied yet. According to the regulatory body, the National Energy Control Center CENACE (power pool) should provide the procedures but none of them are established. The PV solution cannot be treated as a conventional largescale generation connected to the grid as it is the case for large hydro plants or thermal power plants. Again, the issue of awareness on renewables should be brought up to authority levels.
SCG is coming to an agreement with EEPG to consider the whole urban development as a single user. A twoway meter will be installed at the secondary side of the transformer and the tariff applied will be similar to an industrial user. Internally, the administration of SCG will allocate the total costs and sales according to the values measured at each individual home. PV systems will include also a twoway meter that will register both the energy supplied and consumed.
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A careful administration and follow up should be established to keep track of the balance of each user and of the total houses because all income from the energy delivered to the grid should be saved to be used later for the replacement and operation and maintenance costs of the PV systems, including the administration costs and the depreciation of the systems after their lifetime.
A procedure should be agreed with EEPG to claim for the energy delivered to the grid. According to the regulations the power utility should account for that in the national power pool and the local generation should be considered as an independent power producer (IPP). This needs to be worked out still since there is no previous experience on the application of grid connected renewable distributed generation in Ecuador.
CONCLUSIONS
The supply of energy in islands represents an excellent opportunity for renewable energies, since the use of diesel generating plants implies not only a very high cost of operation and maintenance but also has an effect in the environment due to GHG emissions and risk of oil spill in the transportation of fuel.
The paper presents a case of private urban development housing in the Galapagos Islands of Ecuador, where isolated photovoltaic systems will be used to supply the full load of the dwellings and any excess will be sold back to the grid. In this case, the grid acts as a back up.
Initiatives of local and international organizations favor the introduction of renewable energies at the official level in the Galapagos islands with the coming into service of renewable energy projects. In accordance with that purpose, the private initiative in Santa Cruz Gardens helps to build up trust in the technology. Results of the study show that although the initial cost of the systems are large compared to the grid extension, the benefits gained with the operation cover the costs and service in the lifetime. With the application of the feedin tariff of USD 0,312 per kWh, the depreciation costs are also accounted for. Diesel fuel savings in the 20year period sum up to 122.270 gallons (463000 liters); emission of 290 tons of CO2 will be reduced.
The main benefit of the project is the raise of awareness in the islands to the use of photovoltaic technology in a distributed way, where each owner accepts its commitment with the environment and serves as an example of the new attitude towards the use of energy and energy efficiency.
Along with the installation of the system other aspects have to be taken into consideration for the effective application of the renewable energy solution in Galapagos, since this is the very first project in the country where distributed generation at a private premise will come into service. One of them is the application and viability of the feedin tariff scheme; other is the introduction of real fuel costs to account for externalities, and the presentation of proposals for energy efficiency in electrical appliances and land use regulations. Finally Santa Cruz Gardens will serve as a demonstration project which could be replicated in other parts of the islands and in the continental Ecuador.
It is always difficult to open the road to new ways of doing things and beat the inertia of the past but this project proves when things are done the right way, they finally the barriers are overcome.
ACKNOWLEDGEMENTS
The author wishes to thanks the Post Graduate Programme Renewable Energy PPRE of the University of Oldenburg for the permanent support in maintaining the Student Network and keeping all of us together in the cause of renewables in the world.
The strong commitment of the private developers of Santa Cruz Gardens has helped succeed in the realization of the project and the author is honored to have participated in this idea.
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The Ministry of Energy and Mines of Ecuador is also committed in the introduction of renewable energies and especially in the isolated and rural areas and the author is working together with the people in charge for this purpose.
Being part of the academics as a professor in the subject of Renewable Energies at the Universidad San Francisco de Quito has helped enhancing the awareness of the environmentally friendly technologies among the students and future users and promoters.
REFERENCES
Sanchez S., “Energías Renovables: Conceptos y Aplicaciones, Texto de Consulta”. WWF, Fundación Natura, Ministry of Energy and Mines, July 2004. CONELEC statistical data. www.conelec.gov.ec CENACE, www.cenace.gov.ec Efficacitas Consulting. Capacity Building of ElecGalapagos for the introduction of Renewable Energies, Report May 2006. ENERPRO Photovoltaic Systems Design Software. 2006 ERGAL Project. UNDP, Ministry of Energy and Mines. Reports and Project results. 2005, 2006. Charles Darwin Foundation. www.darwinfoundation.org/downloads/jessica_impacto_biologico.pdf Santa Cruz Gardens project presentation. www.santacruzgarden.com/index.html HOMER Software, NREL, 2006.
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