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First the link to this week’s complete list as HTML and as PDF.
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In most Bible editions the word “Millo”
remains untranslated. There are several hypotheses what Jerusalem monument this term may signify and like many I have found none of them convincing. It looks like McKinny et al. have finally found the answer.
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Three out of the four authors of Gibb et al. do not work in science or industry but for a political lobbying NGO and the last author is no specialist. That alone does not tell us anything about the content of the article, but it does suggest close and critical reading. The text exclusively speaks about air source installations but an undisclosed fraction of the data stems from ground source pumps.
The authors consider any COP above 1 to be an improvement. Not so. With the current sources of electricity generation any COP below 3 will not lower but raise carbon emissions in the main heating season. The assumption is not even true for direct electric heating as the alternative. Heat pumps generate little more than warm air – for the systems described here for China, Canada and the US it’s strictly nothing but – while direct heating offers many options using large fractions of radiative heat. The same subjective feeling of warmth can be achieved at significantly lower air temperatures and conductive losses.
Even if very low COPs are only achieved on few days of the year, the whole system has to be dimensioned for those peaks and will be significantly oversized all the rest of the time with all the disadvantages and extra losses that entails.
The diagrams show point values for single days. The averages are calculated across these data points, most of which are sampled near the upper end of the temperature range. Even if that were not the case, a correctly calculated SCOP has to be weighted by the power output and will be strongly skewed towards the coldest days. This is not done here making the tabulated “averages”
misleading and meaningless.
Omitting the three geographically Scandinavian countries (i.e. without Denmark) the stated implication of figure 1 is turned into its opposite. Scandinavia has an abundance of cheap hydroelectricity skewing the profit analysis and reducing its transferability. Heat pumps are a very good choice where they can be well integrated by design, but against their claimed conclusion Gibb et al. mainly support the arguments of the critics against general application.
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Contrary to what Mithen et al. imply, a single exceptional site in otherwise culturally different surroundings does not signify cultural homogeneity over a large region. Using wildly anachronistic terms it rather reminds of a missionary hub, a colonial government centre, or a commercial exclave. As the authors rightly say, any understanding of the phenomenon has to be preceded by a chronology precise enough to ascertain the direction of influence.
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