This product from Alphasense offers a lower cost solution against NDIR based CO2 sensors which are very expensive.

“The Alphasense patented carbon dioxide sensor is a world first in CO2 monitoring:

Requires no power
Operates at room temperature
One sensor measures from 500ppm to 95% CO2
Small size
Low cost
Simple interfacing

Using the potentiometric measuring principle with our patented silver halide solid state electrolyte, this sensor does not have the high power requirement or high price tag of NDIR technology. This sensor is ideal where low cost and low power are critical for CO2 measurement.

This sensor is the result of seven years of research and development, and this work continues. While not as accurate as NDIR, and not suitable for IAQ measurements, this sensor is ideal for safety alarms, combustion gas monitoring and high CO2 process monitoring.”

If you are looking for an affordable low power solar cell here is what Farnell Philippines can offer. A 10 W solar cell for 7,792 pesos which is manufactured in China by RALOSS. It’s enough for charging your standard lead acid battery for emergency lighting purposes.

Manufacturer: RALOSS
Manufacturer Part No: SR10-36

SOLAR PANEL, 10W
Depth, external: 28mm
Length / Height, external: 356mm
Power, output: 10W
Width, external: 352mm

If you are looking for a cheap and accurate temperature sensor, use the LM35 silicon temperature sensor. It’s good for general temperature sensing like ambient temperature monitoring, incubator temperature sensing, overheat protection and even on fire alarms. The LM35 is a voltage output temperature sensor which has a response of 10 millivolts per degree centigrade and it is accurate within 0.5 degree centigrade. It can operate at -55 C to +150 C and it accepts supply voltages from 4 volts up to 30 volts. The current cost of the LM35 in Philippines is about 100 pesos. Ease of use and simple circuitry is a good feature of the LM35 since all you need to do is power up the unit and just connect the output pin to a digital tester or a microcontroller and you have an instant digital thermometer.