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Sizing a rainwater harvesting cistern by minimizing costs

Publication ,  Journal Article
Pelak, N; Porporato, A
Published in: Journal of Hydrology
October 1, 2016

Rainwater harvesting (RWH) has the potential to reduce water-related costs by providing an alternate source of water, in addition to relieving pressure on public water sources and reducing stormwater runoff. Existing methods for determining the optimal size of the cistern component of a RWH system have various drawbacks, such as specificity to a particular region, dependence on numerical optimization, and/or failure to consider the costs of the system. In this paper a formulation is developed for the optimal cistern volume which incorporates the fixed and distributed costs of a RWH system while also taking into account the random nature of the depth and timing of rainfall, with a focus on RWH to supply domestic, nonpotable uses. With rainfall inputs modeled as a marked Poisson process, and by comparing the costs associated with building a cistern with the costs of externally supplied water, an expression for the optimal cistern volume is found which minimizes the water-related costs. The volume is a function of the roof area, water use rate, climate parameters, and costs of the cistern and of the external water source. This analytically tractable expression makes clear the dependence of the optimal volume on the input parameters. An analysis of the rainfall partitioning also characterizes the efficiency of a particular RWH system configuration and its potential for runoff reduction. The results are compared to the RWH system at the Duke Smart Home in Durham, NC, USA to show how the method could be used in practice.

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Published In

Journal of Hydrology

DOI

ISSN

0022-1694

Publication Date

October 1, 2016

Volume

541

Start / End Page

1340 / 1347

Related Subject Headings

  • Environmental Engineering
 

Citation

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Pelak, N., & Porporato, A. (2016). Sizing a rainwater harvesting cistern by minimizing costs. Journal of Hydrology, 541, 1340–1347. https://doi.org/10.1016/j.jhydrol.2016.08.036
Pelak, N., and A. Porporato. “Sizing a rainwater harvesting cistern by minimizing costs.” Journal of Hydrology 541 (October 1, 2016): 1340–47. https://doi.org/10.1016/j.jhydrol.2016.08.036.
Pelak N, Porporato A. Sizing a rainwater harvesting cistern by minimizing costs. Journal of Hydrology. 2016 Oct 1;541:1340–7.
Pelak, N., and A. Porporato. “Sizing a rainwater harvesting cistern by minimizing costs.” Journal of Hydrology, vol. 541, Oct. 2016, pp. 1340–47. Scopus, doi:10.1016/j.jhydrol.2016.08.036.
Pelak N, Porporato A. Sizing a rainwater harvesting cistern by minimizing costs. Journal of Hydrology. 2016 Oct 1;541:1340–1347.
Journal cover image

Published In

Journal of Hydrology

DOI

ISSN

0022-1694

Publication Date

October 1, 2016

Volume

541

Start / End Page

1340 / 1347

Related Subject Headings

  • Environmental Engineering