Comments on: Home Fuel Cell Maker ClearEdge Power Adds On $11M

By: Home Fuel Cell Maker ClearEdge to Tackle Korea

Home Fuel Cell Maker ClearEdge to Tackle Korea — Tue, 08 Jun 2010 20:16:22 +0000

[...] of late last year, ClearEdge had raised $55 million in venture capital, and in January 2010 the company added on another $11 million in equity financing. Investors include Kohlberg Ventures, Applied Ventures and Big Basin [...]

By: 10 Fuel Cell Startups Hot on Bloom Energy’s Trail

10 Fuel Cell Startups Hot on Bloom Energy’s Trail — Mon, 22 Feb 2010 19:50:25 +0000

[...] and heat to homes and small businesses. It’s raised about $55 million in venture capital, and most recently landed $11 million in January, with investors including Kohlberg Ventures, Applied Ventures, Big Basin Partners. ClearEdge has [...]

By: Chris Kaiser

Chris Kaiser — Tue, 02 Feb 2010 00:18:31 +0000

Brandon, I understand what you are asking, but it's not semantics. Let's forget the car analogy for now and just focus on the wording. Saying "generate five kilowatts of power per hour" could mean that in the time frame of 1 hour a device might generate 5 kW of power for 1 second (or .1 second, or .00000000001 second), because power is an instantaneous measure. So in that hour, the device produce 5 kW for 1 second, which means it produced .0014 kWh.

However, if you say "five kilowatt-hr of energy per hour" you mean that it produced 5 kW of power for all 3600 seconds in an hour (You could also meant that it produced 10 kW for half an hour, or 20 kW for 15 minutes in the hour, Power multiplied by time).

Basically, energy is power multiplied by time. It isn't semantics, it's math.

Does that make any sense?

By: Brandon - Greenzu

Brandon - Greenzu — Mon, 01 Feb 2010 23:50:20 +0000

Alex or CKmapawatt -

I get the difference between a kW and a kWh. But I do not get the semantic difference of: “generate five kilowatts of power per hour” and "generate five kilowatts of power" or "five kilowatt-hr of energy per hour".

Are you just nit picking the author's wording, or is there actual a real difference here that I'm missing?

For example, to use the car analogy above, if I go 60 mph for an hour then I "go 60 miles per hour." That is what the author said. How is saying (to apply your correction): I "go 60 miles" or I "go 60 mph of distance per hour" substantively different?

Note - I'm not trying to bust your chops either. This is a semantic distinction many have made that has long eluded me.

By: CKmapawatt

CKmapawatt — Tue, 26 Jan 2010 17:43:16 +0000

Alex,
You stole my comment. For those who may be confused on this topic, a Watt is an instantaneous measure of power, it’s a rate (Joule/Sec). It’s just like when you glance at your speedometer to see how fast you are going. When you look at the speedometer, your instantaneous speed is the rate you are going (miles/hr.) In order to get the total energy something produces you need to multiply the instantaneous rate (power in watts) by the amount of time that something produced that rate at (time in hours) to get the total energy in watt-hours. (or for calculus fans, take the integral of the energy vs. time curve)

I’ve written a blog post on the topic of “What is a kWh”:
http://blog.mapawatt.com/2009/03/12/what-is-a-kilowatt-hour-aka-kwh-part-1/

By: Josie Garthwaite

Josie Garthwaite — Tue, 26 Jan 2010 15:15:26 +0000

fixed - thanks for keeping me on my toes, alex

By: alex

alex — Tue, 26 Jan 2010 06:40:37 +0000

If you are going to report on power generation devices, please get the terms correct. You do not "generate five kilowatts of power per hour", you generate five kilowatts of power, or five kilowatt-hr of energy per hour.