SolarWaterHeater - Revision history

Tom Griffing: /* Design */

2016-05-16T11:33:59Z

Design

← Older revision		Revision as of 11:33, 16 May 2016
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	First, calculate the resistance of the hot water heater heating element, then the solar supply voltage to match this resistance and finally, the number of panels necessary for heating the water.		First, calculate the resistance of the hot water heater heating element, then the solar supply voltage to match this resistance and finally, the number of panels necessary for heating the water.

			UPDATE May 16, 2016: I purchased two 10Amp SSRs, heat sincs and thermal grease and assembled them as shown in the drawing above. It worked well for a couple of weeks, then one of the SSRs quit working with output always closed (bad failure for this application). Now, I have ordered 25 Amp replacements.

	=Test Case=		=Test Case=

Tom Griffing: /* Design */

2016-04-13T03:32:48Z

Design

← Older revision		Revision as of 03:32, 13 April 2016
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	I found some documentation about running hot water heaters from solar power on this web page:		I found some documentation about running hot water heaters from solar power on this web page:

	[http://waterheatertimer.org/Convert-AC-water-heater-to-DC-water-heater.html]		[http://waterheatertimer.org/Convert-AC-water-heater-to-DC-water-heater.html Convert AC hot water heater to DC]

	This is the schematic for a two-element water heater (a single element water heater would use only the top part):		This is the schematic for a two-element water heater (a single element water heater would use only the top part):

Tom Griffing: /* Design */

2016-04-13T03:31:39Z

Design

← Older revision		Revision as of 03:31, 13 April 2016
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	Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.		Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.

			I found some documentation about running hot water heaters from solar power on this web page:

			[http://waterheatertimer.org/Convert-AC-water-heater-to-DC-water-heater.html]

	This is the schematic for a two-element water heater (a single element water heater would use only the top part):		This is the schematic for a two-element water heater (a single element water heater would use only the top part):

	[[Image:WaterHeaterDiagram2.png\|400px]]		[[Image:WaterHeaterDiagram2.png\|400px]]

	IMPORTANT: The thermostats are not rated for DC and will be damaged if DC voltage is applied! To solve this, we must use a Solid State Relay (SSR) to control the DC power to the heating element. Note that the schematic uses a DC-DC power supply and two Solid State Relays (SSR). This arrangement puts only low voltage / low power to the thermostat so it is not damaged.		IMPORTANT: The thermostats are not rated for DC and will be damaged if DC voltage is applied! To solve this, we must use a Solid State Relay (SSR) to control the DC power to the heating element. Note that the schematic uses a DC-DC power supply and two Solid State Relays (SSR). This arrangement puts only low voltage / low power to the thermostat so it is not damaged.

Tom Griffing: /* Design */

2016-04-12T08:53:59Z

Design

← Older revision		Revision as of 08:53, 12 April 2016
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	Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.		Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.

	This is the schematic for the ~~design~~:		This is the schematic for a two-element water heater (a single element water heater would use only the top part):

	[[Image:WaterHeaterDiagram2.png\|400px]]		[[Image:WaterHeaterDiagram2.png\|400px]]

Tom Griffing: /* Design */

2016-04-12T08:49:27Z

Design

← Older revision		Revision as of 08:49, 12 April 2016
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	Most electric hot water heaters for household use heat water using a resistive heating element immersed in the water and a simple bi-metallic thermostat. In the United States, they are usually powered by either 120 VAC or 240 VAC. The thermostat usually employs a bimetallic strip with electrical contacts to interrupt the electricity once the desired temperature has been reached and establish electricity flow when the water temperature drops below a threshold.		Most electric hot water heaters for household use heat water using a resistive heating element immersed in the water and a simple bi-metallic thermostat. In the United States, they are usually powered by either 120 VAC or 240 VAC. The thermostat usually employs a bimetallic strip with electrical contacts to interrupt the electricity once the desired temperature has been reached and establish electricity flow when the water temperature drops below a threshold.

	~~IMPORTANT: The~~ thermostats ~~are not rated for DC and will be damaged if DC voltage is applied! To solve this, we must use a Solid State Relay (SSR)~~ to ~~control~~ the ~~DC power to~~ the heating element.		Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.

	~~Tall water heaters often employ two heating elements~~ and ~~thermostats~~ to ~~heat~~ the ~~upper~~ and ~~lower sections of the tank~~. ~~Shorter water heaters usually have~~ only ~~one heating element~~.		This is the schematic for the design:

			[[Image:WaterHeaterDiagram2.png\|400px]]

			IMPORTANT: The thermostats are not rated for DC and will be damaged if DC voltage is applied! To solve this, we must use a Solid State Relay (SSR) to control the DC power to the heating element. Note that the schematic uses a DC-DC power supply and two Solid State Relays (SSR). This arrangement puts only low voltage / low power to the thermostat so it is not damaged.

	First, calculate the resistance of the hot water heater heating element, then the solar supply voltage to match this resistance and finally, the number of panels necessary for heating the water.		First, calculate the resistance of the hot water heater heating element, then the solar supply voltage to match this resistance and finally, the number of panels necessary for heating the water.

	~~[[Image:WaterHeaterDiagram.png\|400px]]~~

	=Test Case=		=Test Case=

Tom Griffing: /* Design */

2016-04-04T03:52:20Z

Design

← Older revision		Revision as of 03:52, 4 April 2016
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	Most electric hot water heaters for household use heat water using a resistive heating element immersed in the water and a simple bi-metallic thermostat. In the United States, they are usually powered by either 120 VAC or 240 VAC. The thermostat usually employs a bimetallic strip with electrical contacts to interrupt the electricity once the desired temperature has been reached and establish electricity flow when the water temperature drops below a threshold.		Most electric hot water heaters for household use heat water using a resistive heating element immersed in the water and a simple bi-metallic thermostat. In the United States, they are usually powered by either 120 VAC or 240 VAC. The thermostat usually employs a bimetallic strip with electrical contacts to interrupt the electricity once the desired temperature has been reached and establish electricity flow when the water temperature drops below a threshold.

			IMPORTANT: The thermostats are not rated for DC and will be damaged if DC voltage is applied! To solve this, we must use a Solid State Relay (SSR) to control the DC power to the heating element.

	Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.		Tall water heaters often employ two heating elements and thermostats to heat the upper and lower sections of the tank. Shorter water heaters usually have only one heating element.

Tom Griffing: /* The test design is as follows */

2016-03-31T02:31:19Z

The test design is as follows

← Older revision		Revision as of 02:31, 31 March 2016
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	[http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm Earth Temperature Source]		[http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm Earth Temperature Source]

	Calculate the energy required to raise 40 gallons of water from the Dallas ground temperature (19.5 degrees C) to the hot water temperature (~ 51.6 degrees C):		Calculate the energy required to raise 40 gallons of water from the Dallas ground temperature (67 degrees F or 19.5 degrees C) to the hot water temperature (125 degrees F or 51.6 degrees C):

	40 Gallons = 151,416 cc		40 Gallons = 151,416 cc

Tom Griffing: /* Summary */

2016-03-31T02:27:38Z

Summary

← Older revision		Revision as of 02:27, 31 March 2016
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	=Summary=		=Summary=

	~~It works!~~		All the theory sounded good, but the results are what counts. I connected the solar power to the hot water heater and left it running all day on March 26th and in the evening, I had a shower in piping hot water.

			Now, that's results.

Tom Griffing: /* The test design is as follows */

2016-03-31T02:25:34Z

The test design is as follows

← Older revision		Revision as of 02:25, 31 March 2016
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	6 panels at max output produce		6 panels at max output produce

	6 * 230 W = 1.380 kw		6 * 230 W = 1.380 kw

	The average water temperature will be the same as the ground temperature, as shown in this illustration:		The average water temperature will be the same as the ground temperature, as shown in this illustration:
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	Calculate the energy required to raise 40 gallons of water from the Dallas ground temperature (19.5 degrees C) to the hot water temperature (~ 51.6 degrees C):		Calculate the energy required to raise 40 gallons of water from the Dallas ground temperature (19.5 degrees C) to the hot water temperature (~ 51.6 degrees C):

	40 Gallons = 151,416 cc		40 Gallons = 151,416 cc

	energy to raise temperature by 51.6 - 19.5 = 32.4 degrees C:		energy to raise temperature by 51.6 - 19.5 = 32.4 degrees C:

	1 calorie * 151,416 * 32.4 = 4905878 calories or 20539930 watt seconds or 5.705 kwh		1 calorie * 151,416 * 32.4 = 4905878 calories or 20539930 watt seconds or 5.705 kwh

	Use the power figure above for the 6 panel array to calculate the time required to heat the water:		Use the power figure above for the 6 panel array to calculate the time required to heat the water:

	5.705 kwh / 1.380 kw = 4.134 hours		5.705 kwh / 1.380 kw = 4.134 hours

	=Summary=		=Summary=

	It works!		It works!

Tom Griffing: /* The test design is as follows */

2016-03-31T02:25:03Z

The test design is as follows

← Older revision		Revision as of 02:25, 31 March 2016
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	Supply voltage = R * I = 15.1 * 9.5 = 143.45 Volts		Supply voltage = R * I = 15.1 * 9.5 = 143.45 Volts
	#panels = Supply voltage / Panel voltage = 143.45 / 24 = 5.9 Panels		#panels = Supply voltage / Panel voltage = 143.45 / 24 = 5.9 Panels

			6 panels at max output produce

			6 * 230 W = 1.380 kw

	The average water temperature will be the same as the ground temperature, as shown in this illustration:		The average water temperature will be the same as the ground temperature, as shown in this illustration:
Line 57:		Line 61:
	[http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm Earth Temperature Source]		[http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm Earth Temperature Source]

	Calculate the energy required to raise the water ~~from~~		Calculate the energy required to raise 40 gallons of water from the Dallas ground temperature (19.5 degrees C) to the hot water temperature (~ 51.6 degrees C):

			40 Gallons = 151,416 cc
			energy to raise temperature by 51.6 - 19.5 = 32.4 degrees C:

			1 calorie * 151,416 * 32.4 = 4905878 calories or 20539930 watt seconds or 5.705 kwh

			Use the power figure above for the 6 panel array to calculate the time required to heat the water:

			5.705 kwh / 1.380 kw = 4.134 hours

	=Summary=		=Summary=

	It works!		It works!