Hydro Resource

Estimation of the available thermal and potential energy in the Irvine at Newmilns?

As society transitions to a 100% renewable energy system all possible local sources of energy must be evaluated to minimize unnecessary load on the Electricity Distribution Network.

Estimation logic

Data on mean daily flow rate from the National River Flow Archive [1], at a monitoring station in Newmilns, was used along with monthly mean temperature data from the Scotland River Temperature Monitoring Network [2], at a monitoring station just north of Newmilns on the river Ayr.

With this data pre-processed a simple script was developed within MATLAB to evaluate the daily mean thermal energy available. This script subsequently uses trapezoidal integration to yield the likely thermal energy available during the winter.

Weather year sensitivity

The same evaluations were undertaken for the three most recent years and minimal variation to the below presented 2020-2021 results was found. Thus, the analysis is not sensitive to variations on weather year and as such can be considered representative of likely future performance.

NB: A conservative estimate of the available thermal energy in the flow was taken with estimation based on reducing the down stream flow temperature to half o the upstream flow temperature. Primarily because it would be detrimental to flora and fauna downstream to reduce the flow temperature further. Moreover, all data presented in this section is exclusive of losses associated with extraction and conversion. However, given the initial highly conservative estimation of available energy vs total energy in flow it is likely that the data presented is a suitable guide for further investigation and development.

Visualizing mean daily flow rate as a function of time as a function of time

Figure 1: Daily Mean Flow Rate at Irvine River

Newmilns is located fairly high in the watershed of the river Irvine and has a catchment area of just seventy-five square kilometers. As such the flow rate is highly variable and frequently falls to very low levels, as shown in figure 1. This has a strong impact on the subsequent analysis.

Visualizing Thermal available energy as a function of time

Figure 2: Thermal Power Available at Irvine River

As shown in figure 2, the dominant effect of flow rate is seen; with significant variations in available Thermal energy in the rivers flow despite the small temperature variations and generally low flow temperatures during the winter months. The above plot is based on reduction of the down stream temperature to half of that of the current upstream temperature. No estimation of losses during extraction.

Idealized Avalible Energy as a proportion of Current Demand

Figure 3: Winter Thermal Demand

Based on the current Industrial Demand Estimation presented the above time series of available power, once integrated, can be visualized as a proportion of current industrial low-grade thermal energy use, see figures below. With available thermal energy just less than 25% of current consumption, as shown in figure 3.

Unfortunately, this result is considered a hard no; while this represents a non trivial proportion of demand the cost of plant and thermal distribution network were deemed to make further pursuit of this resource financially inviable.

Hydro Kentic Reasource

Figure 4: Representative run of river hydro installation

Figure 5: Satellite View of the Irvine at the Industrial site in Newmilns

The question was raised as to whether the Hydro kinetic resource in Irvine's flow in Newmilns could be used to power the industrial loads considered. While there is in theory energy available in the flow. Run-of -river hydro schemes (see Figures 4 for representative scale of installation) required significant civil engineering works and as can be seen in the satellite photo in Figure 5 above the banks of the Irvine in the vicinity of the Industrial district in question in Newmilns already have significant urbanization. It was concluded that any attempt extract this energy would be both impractical form a planning perspective and inviable from a financial perspective.

Conclusions on the Resource in the River Irvine at Newmilns

Unfortunately, the available thermal energy is too small a fraction of demand to warrant further development.
This is primarily due to Newmilns' location relatively high in the river Irvine watershed and the associated variability of flow rate.
While there may be energy available in the Irvine for extraction via low head hydro the scale of infrastructure required is prohibitive.
Despite a hard no on the thermal energy in the Irvine the estimation logic developed and the strategy taken is highly flexible and could be used for any other river.

References:

[1] National River Flow Archive, nrfa.ceh.ac.uk/ [Accessed 8 May 2023] .

[2] “Scotland River Temperature Monitoring Network (SRTMN).” Scottish Government, 8 Sept. 2021, www.gov.scot/publications/scotland-river-temperature-monitoring-network-srtmn/ [Accessed 8 May 2023].

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