44 • ROCK products • March 2018 www.rockproducts.com
Charleston Stone
charges made up 42 percent of Charleston Stone's electric
bill in 2016.
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CMEC has offered to assist the quarry in managing demand
by providing real-time access to meter data, which would
show 15-minute interval demand. This would provide the
means for Charleston Stone to observe their demand and
adjust operations to reduce demand charges. The co-op is
offering to pay about half the cost of setting up this capabil-
ity. Charleston Stone has not taken CMEC up on the offer yet,
but may do so once all the changes to the crushing operation
have been made.
The projected annual energy cost for the new electric rock
crusher is expected to be higher than diesel when diesel is at
historically low prices, and much lower than diesel when it
is at historically high prices (see Figure 8). At today's diesel
price, which is slightly higher than $2.50/gal., Charleston
Stone could see energy savings of almost $5,000 per year.
Any reduction in energy costs will be welcome, of course, but
it is clear that the change in energy costs is just a fraction of
the financial benefits Charleston Stone should realize from
increased productivity and product quality. The company
expects that the net result of more stable operating costs,
increased productivity, and reduced downtime will make
them more competitive. The company should be able to retain
the existing workforce and even add up to five new employees
as they expand production over the next three years.
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FIGURE 8: Diesel crusher vs. electric crusher energy
cost/year at different prices per gal.
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