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Talk:Motion sensor controlled vending machines

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The excel spreadsheet and appropedia page have different electricity prices (0.08$/kWh and 0.075kW$/kWh)is there a reason for this? --R.Kenny 02:35, 11 February 2010 (UTC)

Changed the cost of electricity on Appropedia page from 0.075$/kWh to 0.08$/kWh. If you would rather be consistent with 0.075$/kWh, you can change them on both. --C.Rea 02:37, 11 February 2010 (UTC)

Is the 15 minute turn off time inherent in the technology or can it be programmed? If it can be programmed is there a shorter time period that could lead to increased savings? --R.Kenny 02:35, 11 February 2010 (UTC)

The 0.222kg/kWh do you have reference for this? --R.Kenny 02:35, 11 February 2010 (UTC)

Alternative energy saving techniques are mentioned in your executive summary which is a great idea, why did you not put this on your appropedia page? Also maybe make it more visible in your spreadsheet. --R.Kenny 04:19, 11 February 2010 (UTC)

The legend on the input page is awkwardly formatted. --R.Kenny 04:19, 11 February 2010 (UTC)

What does green highlighting in the spreadsheet mean? --R.Kenny 04:19, 11 February 2010 (UTC)

It might be worth re-arraging your spreadsheet so that it can be printed.--R.Kenny 02:35, 11 February 2010 (UTC)

A minor note - the unit kilowatt-hour is written kWh, with attention to upper/lower case letters. --C.Rea 02:37, 11 February 2010 (UTC)

Will "Additional Maintenance Costs" ever need to be factored in (currently they are $0 for every year)? If not, consider removing that row. --C.Rea 02:37, 11 February 2010 (UTC)

In your "Projected Savings" tab, in the "Economics" section, the title "Difference in Net Cash Flows" is somewhat confusing. I understood what it meant after looking at the numbers, but I would suggest making the title a bit more clear. Something like "Annual cash balance" may be better suited. --C.Rea 02:37, 11 February 2010 (UTC)

  • An addition to the above: this should be "Net cash flow". Note that this spreadsheet looks at the motion sensor as an investment, and therefore that "Net cash flow" is more appropriate than "difference in net cash flows" (which looks at both types of vending machines as investments compared to each other).C.Law 13:24, 11 February 2010 (UTC)
  • Assumption 2 is incorrect. There are 365 days/year, and 24 hours/day, meaning 8760 hours/year. 52 weeks/year is a rounded value. Very technically, there are 8766 hours/year (if you automatically include leap years) C.Law 13:24, 11 February 2010 (UTC)

Comments on Appropedia Information Page (sorry if there are repeats from above):

  • Please define or re-word "high-head-pressure". I know what you mean, but its awkwardly worded. --M. Urquhart 02:46, 11 February 2010 (UTC)
  • Choose consistent spacing between both sentences (some have one space at the beginning, others have two) and paragraphs (breaks could be used more effectively). --M. Urquhart 02:46, 11 February 2010 (UTC)
  • The sensor cannot differentiate between the wall and the person, it only measures changes in the IR radiation in its atmosphere (which you do go on to explain.) I'd be careful how you word the second paragraph in 'Passive Infrared Sensors' to make their operation a little more clear. Or, just say they measure the difference and link to the Wikipedia article. Your paper is on vending machines, not PIR sensors. --M. Urquhart 02:46, 11 February 2010 (UTC)
  • Watch units: kg (not Kgs), kWh (not Kwh), and express the costs as $/MW in the 'Health Effects' section. --M. Urquhart 02:46, 11 February 2010 (UTC)

Comments on Spreadsheet (sorry if there are repeats from above):

  • In 'Introduction', the word 'novelty' makes the machine seem like a toy. Remember this is for a business and makes them money. Take it seriously --M. Urquhart 03:39, 11 February 2010 (UTC)
  • Exclaimation points are intimidating; don't cell at me, I'm using your work! Make the instructions stand out another way. --M. Urquhart 03:39, 11 February 2010 (UTC)
  • Where the legend introduces the colour coordination, I'll read what the inputs are when I see the colour of the cell. Perhaps you want to include an Instructions section that guides the user where to enter information for their project? Don't do it in the legend though. --M. Urquhart 03:39, 11 February 2010 (UTC)
  • I like the separation of the inputs from the calculations. Good work. --M. Urquhart 03:39, 11 February 2010 (UTC)
  • References and assumptions need to be organized much better. Each assumption has a number and source on the 'Assumptions' sheet, but these don't match up with any indicators in the calculation sheets.--M. Urquhart 03:39, 11 February 2010 (UTC)
  • Watch decimal places of numbers. Remember these are estimated from average usage data; I don't need to know energy usage to two decimal places. --M. Urquhart 03:39, 11 February 2010 (UTC)
  • Double-check the amount of carbon emitted per kWh. That sounds really high to me... There's no source for me to check that. --M. Urquhart 03:39, 11 February 2010 (UTC)
  • Rather than being an assumption, make the hours of operation editable by the user (in hours, days, weeks, whatever they want). No one can say 'I use this 8000 hours per year", they say it runs 24 hrs per day.--M. Urquhart 03:39, 11 February 2010 (UTC)
  • The example at the beginning assumes 30 mins installation time, but the calculation (and assumption) says 1 hr. --M. Urquhart 03:39, 11 February 2010 (UTC)
  • Unless the colours have a purpose, it would be my preference for them to not be on the 'Projected Savings' sheet at all. They attract my attention to what I found out is something I don't care about. Use gridlines and bold/underline to direct emphasis, unless the colours have a legend.--M. Urquhart 03:39, 11 February 2010 (UTC)
  • Your method of calculating discounted cash flow is incorrect. Discounted cash flow is created by adjusting your net cash flow ("Difference in net cash flows" on the sheet - Projected Saving Row 9) for the risk-free rate of return in Row 11. Thus, Row 12 should reference Row 9, not Row 10. The Cumulative discounted cash flow (Row 13) is thus also incorrect because it references Row 12. As it stands, Row 12 is your cumulative discounted cash flow, and Row 13 is your cumulative cumulative net cash flow (which has no meaning). This has also lead to an error in your net present value.C.Law 13:24, 11 February 2010 (UTC)
  • Your "Cumulative energy reduction frm modified operation (Kwh) (∑(E1-E2))" is incorrect. Row 26 references the energy savings in the baseline year (which do not happen: that assumption means that you started saving energy a year before you installed the motion sensor). To further demonstrate this point, multiply your "cumulative energy reduction from modified operation" by the price of electricity. This value should match your "Saving from the modified operation ($ per year) (S=A-B-M)" in Row 5.C.Law 13:24, 11 February 2010 (UTC)
  • As a follow-up to the previous point, you also count greenhouse gas emissions in the previous year. Ensure that the baseline is deleted from this calculation.C.Law 13:24, 11 February 2010 (UTC)
  • There is a spelling error in your spreadsheet, in the Projected Savings Tab, Cell B25 - the word 'assumptions' --C.Rea 00:00, 10 March 2010 (UTC)