Schematic for a "smart" solar shades concept.
Project data
Authors Luke Johnston
Location Michigan, USA
Status Designed
Cost USD 12.69
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This page contains methods on the topic of "smart" solar shades using PV.

To see the literature review of this topic, click here

The "Smart" solar shade project is designed to be a two step process: first to simulate the potential savings by utilizing an automated window shade system is utilized to heat or cool a room, followed by then demonstrating such a system experimentally.

Simulation[edit | edit source]

Please spend some time thinking about this
after you build and have a working prototype
how do we move that towards publication
see email in relation to simulation ideas

Experiment[edit | edit source]

Hardware[edit | edit source]

Design Considerations[edit | edit source]

Component Sizing[edit | edit source]

Electric Motor[edit | edit source]

Servo, stepper, and DC motors were considered for the window blind actuation. The cheapest option was found to be a geared hobby motor utilizing a potentiometer for position feedback. The GM3 geared hobby motor provides up to .34 Nm of torque at ultracapacitor voltage.

Ultracapacitor[edit | edit source]

The power storage component was fortunately given from a cost standpoint, but unfortunate from an engineering standpoint. It is governed by the relationship of current to the change in voltage in a capacitor.

[math]\displaystyle{ i(t)= C\frac{\mathrm{d}v(t)}{\mathrm{d}t} }[/math].

Given that the voltage range of the ultracapacitor to be 1.0-2.7V dictated by the maximum ratings of the ultracapacitor and minimum ratings of the DC-DC converter, this means the voltage may drop 1.7V. This equates to approximately 6.9 KJ of energy, enough to run the selected motor at its maximum power at 3V for over an hour - much longer than is needed.

Link here to all the ultracap info for the models we are using.
PV Panel[edit | edit source]

The PV panel is still yet to be determined, however, it would be best if its open circuit voltage is close to 2.7 volts. This would prevent the ultracapacitor from overcharging no matter what.

DC-DC Converter[edit | edit source]

Given that the Arduino Uno used as the controller in this experiment is powered off of a 5V power source, a method is needed to convert the ultracapacitor voltage. Using Digikey's search feature, a number of DC-DC converters were found to output 5v. The LT1073-5 was selected due to the few number of external components needed, as well as its low required input voltage (1V).

Ultracapacitor Safety[edit | edit source]

Due to the high energy content and discharge rate of the ultracapacitor, considerations must be taken into account to keep the ultracapacitor from being over charged. A relay is put in between the PV panel and ultracapacitor. It is normally closed, so it's default action is to charge the ultracapacitor. However, the Arduino controller has control of the relay and reads in the ultracapacitor voltage as an analog input. If this voltage is deemed to high, the Arduino has control to cut power to the ultracapacitor.

Since there is a potential hazard to use such a large capacitor such as the 3000F Maxwell capacitor used in this experiment, a method is needed to easily and safely discharge the capacitor. A power resistor is put in parallel with the ultra capacitor with a switch in series for this reason. In practice, it may be useful to have this feature for time when users are away from the room for extended periods of time such as vacations.

Hardware List[edit | edit source]

Description Function Model/Part # Supplier Unit Price Quantity URL Comments
DC Motor Blind actuation GM3 5.75 Blind_Number Price for buying 2-20 units
Trimpot Blind position feedback RT10k 1.1 Blind_Number
SPDT Relay Switching motor/cutting charging 3.5 2*Blind_Number +1
SPST switch For discharging ultracapacitor 1
PV panel Power source 1
Ultracapacitor Power storage BCAP3000 E270 T04 Maxwell 1 In hand
Temp sensor Room temperature sensing TMP36 Digikey 1 In hand
Controller Arduino Uno Arduino
Perf board PCB
Project Box Enclosure for components
Misc electronics For DC-DC converter In hand
Power resistor For discharging ultracapacitor Digikey
DC-DC Converter Boost from UC to +5V LT1073-5 Digikey 1
Fuse holder Holds fuse Digikey 1.21 1
Fuse To fuse power from UC Digikey 0.71 3
Misc hardware For mounting components in project box
Wire For wiring components
Diode Circuit protection 1N5817 Digikey 0.42 2

Logic[edit | edit source]

Basic window control logic

A simple high-level control scheme is implemented initially as a proof of concept. It essentially compares the desired temperature to room temperature and opens or closes the blinds based on temperature difference. When the PV panel is decoupled from the ultracapacitor, open circuit voltage of the PV can be taken to determine sunlight. Ideally, transients are expected twice a day in order to decrease power demand.

In future iterations of this project, more complex models may be used. Since the blinds in this system have position feedback, it is possible to operate them at many different angles.

please see notes in email about logic
Page data
Part of MY5970
Type Project
Keywords solar shade, Photovoltaics, pv, energy conservation, blinds, motorized blinds, automatic blinds, temperature sensor, Energy efficiency
SDG Sustainable Development Goals SDG07 Affordable and clean energy, SDG11 Sustainable cities and communities
Authors Luke Johnston
Published 2012
License CC-BY-SA-4.0
Affiliations MTU, MOST
Impact Number of views to this page. Updated once a month. Views by admins and bots are not counted. Multiple views during the same session are counted as one. 205
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