City Oasis is an environmentally friendly convenience station. Although it is just a small place, it can improve people's life from various aspects. Basically, the concept was generated from bring convenience to those who ride to work, so we designed a food kiosk with bathrooms near the bike parking area. In order to reduce the energy consumption of the convenience services, the station equips eco-friendly energy systems, including solar panels, wind generators and motor generators. Thanks to the food service, resting area with plants and motor generators, City Oasis has become a relaxation place for friends meeting and exercises. Passersby can also charge their computer and mobile phones in the station. In the middle of the kiosk is a digital screen which can show the power consumption of the services and the energy contribution from the participants. Those who have exercised on the motor generators would get discount on the services according to the energy they have contributed to the system. Moreover, the grey water is treated and stored to irrigate the plants as well as to fill the sanitation vehicles.
Technical Feasibility
1 Two Systems: power system & grey water system
1.1 Power system
Figure.1 Architecture of the whole system
There are three different types of inputs: PV system, wind turbine system and bike generators. And the outputs are coffee machines, phone chargers and hot water. The figure.1 is the architecture of the whole system.
All the energy stores to the battery bank first, and then the electricity outputs from the battery bank. This could allow customers to use huge amount of electricity in a short time.
1.1.1 Energy consumption
According to http://www.donrowe.com/inverters/usage_chart.html
2 Coffee machines: 1200 Watts*2 = 2400 Watts
2 Microwaves: 1100 Watts*2 = 2200 Watts
Pump of grey water system: 1400 Watts
As can be seen in the chart of wattage calculator http://www.consumerreports.org/cro/resources/images/video/wattage_calculator/wattage_calclulator.html
Electric water heater: 5000 Watts
As a sum, the peak usage of electricity is 11000 Watts. However, not everything keep using in the whole day. It is assumed that the coffee machines, microwaves are used 6 hours per day ( 2 hours for the 3 peak times: before work, lunch time and after work)and electric water heater is used 4 hours ( 2 hours for before work and 2 hours for after work). Therefore, the actual consumption of electricity per day is about
(2.4 kw + 2.2 kw ) * 6 hours + ( 1.4 kw + 5 kw ) * 4 hours = 53.2 kwh
1.1.2 Solar power
Figure.2 The statistics of solar panels. (http://www.ecobusinesslinks.com/solar_panels.htm)
Figure.2 shows that the ordinary peak power is 230 Watts, so the actual power might be 200 Watts. If the panels work 10hours/day(7.00-17.00) and the roof of the kiosk is about 12m2, there should be 12 penals and the generated power of everyday should be 0.2 kw/panel * 12 panels * 10 hours = 24 kwh.
1.1.3 Wind power
Figure.3 Several types of wind generators (http://www.wholesalesolar.com/wind.html)
From http://www.seabreeze.com.au/Graphs/nsw.asp, it can be estimated that the average wind speed in Sydney is about 20 km/h, which is equivalent to 12.4 mph. As in the Figure.3, the whisper 500 generator could produce 538 kwh per month at this wind speed, which means this wind turbine generate more than 538 kwh/month /30 days = 18 kwh per day if it applies in our project.
1.1.4 Bike generator ( motor generator )
Figure.4 Architecture of the bike generator (http://www.instructables.com/id/How-To-Build-A-Bicycle-Generator/)
Figure.4 is the architecture of the bike generator, which contains a motor and a drive belt to convert the exercise energy to electricity and store it into the battery bank. The battery bank and the inverter are shared with solar energy and wind energy.
This article http://pedalpowergenerator.com/buy-bicycle-generator-assembled-pm-motor-pedal-power.htm says that riders could produce 300 Watts every hour. It is estimated that there are ten bikes and each bike is used for 5 hours per day (used by different person). There will be 300 Watts * 5 hours * 10 bikes = 15 kwh produced by the bike generators in the day consumption of electricity.
1.1.5 Energy Supply
According to the above calculations, the total energy supply is 24 + 18 +15 = 57 kwh, which is more than the consumption.
1.1.6 Battery bank
Figure.5 Some types of batteries (http://www.hardysolar.com/solar-battery/)
The main purpose of battery bank is to store the continuous energy and provide it to customers instantly as well as stabilize the voltage of the electricity. Hence, there is no need to make the storage is the same volume of day consumption. The volume to store all the energy at night is enough. During 0.00a.m-6.00p.m, the only continuous energy is the wind power. According to Figure.3, the wind power of this period is about 5kwh. In order to ensure the supply in the daytime, the battery bank needs 3 HSSBBB-AGM-8800-48V. The calculation is as follows (http://www.hardysolar.com/solar-battery/battery-bank-sizing.html):
The depth of discharge is 30% so that the battery will have 2000 life cycles. Our goal is to build a 5000 watt battery bank using 30% discharge cycling the batteries once a day.
3 batteries * 8800 Watts*30% = 7920 Watts > 5000 Watts
This means 3 batteries is enough for our project.
1.2 Grey water system
Figure.6 Architecture of grey water system
The numbers in Figure.6 correspond to following functions:
1. Pre-Filtration: Larger particles like hair and textile fragments are collected. The filter is automatically flushed by a special spray pump - sediments are washed away into the main wastewater drain.
2. Two-fold biological treatment: In the main and secondary recycling chambers the dirt particles are decomposed by bio-cultures. The water is pumped to the next station in three hour intervals.
3. Sediment disposal: The organic sediments which are produced during the recycling process are regularly sucked out from the chambers and diverted into the wastewater drain.
4. UV-Sterilization: On the way to the storage chamber the recycled water flows through a UV-light lamp which disinfects it. The high quality of the water now conforms to the E.U. Directive for Recreational Water.
5. Automatic freshwater feed on demand: Should the supply in the storage unit drop below a certain level, freshwater will automatically be fed into this chamber to ensure there is enough supply for flushing toilets.
Figure.7 Details of one kind of grey water diverter
A government research (http://ga2.er.usgs.gov/edu/sq3action.cfm) reports that 2.5 gallons of water is used every minute when people taking a shower. So the grey water of one day is 2.5*60*4*4=2400 gallons (2 hours before work and 2 hours after work).The grey water diverter in Figure.7 could treat 7000 liters of water per hour, so it is fairly enough for our project. The treated grey water would be stored in a tank and be taken by the cleaning vehicle for the purpose of cleaning the road or washing cars.
2 Price
2.1 Solar panels
According to the Figure.2 the most suitable price of solar panels could be $275 per panel. Therefore, the total cost of solar panels is $275*12=$3300.
2.2 Wind turbines
As is shown in Figure.3 the price is $8553.
2.3 Bike generators
Figure.8 Prices of 300 Watts bike generators
The cheapest one is enough for our project, so the cost is $399*10=$3990.
2.4 Battery bank
From Figure.5, the price of 3 batteries is $5398*3=$16194.
2.5 Grey water system
As is shown in Figure.7, the price of grey water system is $2100.
2.6 Other services
Total costs of all above: $3300+$8553+$3990+$16194+$2100=$34137
Our budget is $100,000, this leaves $65863 for construction of the kiosk, pipe system, electricity system and coffee machines and chargers.
