In the Japanese Way of Tea, charcoal is traditionally burned to heat the water for making matcha. (Where suitable charcoal is unavailable or prohibited, we make do with electric heating elements.) In this project I'm attempting to integrate solar thermal technology into the Way of Tea by using solar vacuum tubes to heat the water while otherwise maintaining the aesthetics of this tradition, including the use of natural materials and deliberate, graceful handling of the utensils.

Because direct sunlight is required to heat the water in solar vacuum tubes, this heating method is most suited to outdoor tea gatherings. Often temporary tea spaces are erected for open-air events. Modern artists have designed temporary tea spaces using a variety of materials - including glass, sheer fabric, and wood - to create the cocoon-like intimacy of a tea room while remaining connected to the outdoor environment. In conjunction with the use of solar thermal technology, this project includes the development and construction of a mobile tea room that provides guests with that sense of simultaneous connection with and disconnection from the outside world while accommodating the solar vacuum tubes' requirement for direct sunlight.

I'm using solar vacuum tubes from Clean Republic. Like a high-quality thermos, they're double-walled containers with a vacuum in between to minimize heat loss. The dark outer coating of the tubes absorbs infrared energy from the sun, while the highly reflective inner layers of steel, aluminum, and copper trap that energy inside.

In ideal conditions, these solar vacuum tubes are said to be able to heat water to boiling in one hour. Under typical conditions they can't necessarily heat water to boiling, but fortunately the ideal water temperature for making matcha is sub-boiling, around 75 degrees Celsius. To monitor the water temperature inside the tubes, I am developing an Arduino-based thermometer using a waterproofed version of the 1-wire DS18B20 digital temperature sensor.