Under the hood



A normal 10 ft x 10 ft x 10 ft room takes about 1,500 watts (W) to heat. This typically heats the air, which rises, goes to the ceiling, comes back down and heats you. Thus, the warmest part of the room is the ceiling, where we spend very little time.

FIG 1. The Haser uses a camera & image processing to find you and track you, similar the Microsoft Kinect shown. Free and open source (FOSS) is available that can do the same thing: Predator (based on OpenCV). Project Sentry Gun is free software that can be used for the actual "point & shoot" (it was written for automating a paintball gun).

FIG 2. Haser then uses movable heat source(s) and sends out collimated (i.e. highly parallel) beams of infrared radiation to target key spots on your body that have already been identified by the sensors.

FIG 3. A peek inside. The cameras feed into the tracking software. The pyrometer (heat sensor) gives a low-resolution thermal image of the room and the person. The microphone is for voice commands, the speaker gives voice output and the WiFi helps is communicate with other devices (& the internet). The controller board does the sensory input processing and moving the IR heads to targets.

FIG 4. One type of Haser head that uses a laser.

FIG 5. Tests with IR laser and thermal sensitive fabric, distances of 3 feet to 12 feet.

FIG 6. Finally, the Rover. A thermal store on a robot platform, it heats up the material inside using electricity, then runs over to  you and emits radiant heat. It isn't as slick as the Haser, but what it does it important, producing heat from the "floor level." This helps with the "ideal" heating profile, as explained further below.



FIG 7. Modes of heat loss. The body needs to lose about 90W which it generates from internal metabolic processes. This is why you need the outside temperature to be about 75F, about 20F less than the 96F of your typical skin temperature. The crucial thing to remember is that all a heating system needs to do is to compensate for the difference between the actual heat loss and the desired 90W. That's why you're ok if you sit right next to a radiant heater or a heat lamp. You get just enough to cover your loss.

FIG 8. Heat gain/loss for a human. Note that as the temperature decreases, most heat loss is via radiation & convection (of which about 75% is via radiation).

FIG. Equation for heat transfer to/from the body via radiation.

FIG 9. Plug in values for a chilly room... this comes to 132W (see hyperphysics.phy-astr.gsu.edu/hbase/thermo/bodrad.html#c1). It is typically 20W - 40W depending on the ambient temperature and the particular individual. Assuming that you are mostly clothed, it will be much less. Assume that the total body surface area is 2 m2 on average and that the Haser can only heat what it sees (line-of-sight), i.e. 1 m2. Assume that half the person's body is unclothed, so the Haser needs to cover 1/2 m2. Thus, 20W over that is 4mW/cm2.

Heating your house

FIG 10. Temperature profiles -- underfloor radiant heating is closest to ideal and is mimicked by the Rover robot that carries a charged PC M (Phase Change Material) of high heat capacity.

FIG 11. Typical convectional heating. Inefficient.

FIG 12. Typical fan heater. Note the intial laminar flow, quickly followed by turbulence. Inefficient.

Visible light, infrared, ultraviolet, radio waves, microwaves, X-Rays and Gamma Rays are all radiation. Some of it is harmful, some of it is not. In general, the higher the concentration of the radiation the more potential for harm (though the body absorbs and transmits different frequencies differently).

FIG 13. Radiation from a normal source (e.g. lamp). Energy diverges in all directions, so the power (actually irradiance) gets exponentially weaker as you move further away. Note how fewer rays pass through the sheet (A) as it moves to the right. This is called the inverse square law.

FIG 14. Lasers are collimated, i.e. focused to be parallel, so they do not diverge (practically) even over great distances. Everything diverges, lasers just diverge very slowly.

FIG 15. Laser safety max permissible exposure (MPE). As long as you are under the curve for a particular wavelength, you're good.

FIG 16. The electromagnetic spectrum. The infrared (IR) region closer to visible light best feels like nice warmth. All radiation (even light) contributes to warming you up. 


Subpages (1): Janea Systems timesheet
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