Waternet can undertake within the watercycle (heat and cold recovery from sources ... The capital recovery factor alpha is determined by the following formula:.
Utilizing marginal abatement cost curves (MAC curves) to strategically plan CO2 reduction possibilities for the water sector: the case of watercycle organisation Waternet 1
Sanderine van Odijk1,2, Stefan Mol2, Robert Harmsen1, André Struker2, Eilard Jacobs2 Utrecht University, Copernicus Institute of Sustainable Development, Utrecht, the Netherlands 2 Waternet, Korte Ouderkerkerdijk 7, 1096 AC Amsterdam, the Netherlands
Keywords: decision making, MACC, climate change mitigation, energy from water
Introduction Due to the current pressures of climate change and resource depletion, a great demand is rising for sustainable sources of energy, especially in densely populated areas such as cities. As many authors have already acknowledged (Frijns et al., 2008; Mol et al., 2010; van der Hoek, 2012; Blom et al., 2010; etc.) the watercycle offers much potential in terms of thermal and chemical energy in order to reduce CO2 eq. emissions, herewith creating value of metabolic urban streams to allow for direct sustainability applications in urban areas. Although the theoretical and technical potential is often highlighted, water utilities might face difficulties translating these to deployable strategies. Often, the insight lacks to compare different CO2 eq. emission abating opportunities with each other. In order to support the decision-making process and to validate the choices made, the methodology of marginal abatement cost curves (MAC curves) can be of assistance. The aim of this research is two folded. First of all, it will highlight the applicability of the MAC curves methodology as a decision support tool for water utilities in their quest for sound CO2 eq. emission reductions strategies. Additionally, the research also sheds light on the costeffectiveness of the CO2 eq. emission abatement of several opportunities, which water utility Waternet can undertake within the watercycle (heat and cold recovery from sources such as waste water and surface water) and outside of the watercycle (renewable energy production through PV and wind). The outline of this paper is as follows: the methodology of MAC curves will be explained after which a practical case for water utility Waternet will illustrate the applicability of MAC curves. Finally, the conclusions of this research will be given. Methods MAC curves are a type of decision support tool that list technical options to their costs of conserved energy values (CCEs), or in the case of CO2 eq. emissions to the costs of conserved CO2 eq. emissions (e.g. euro per ton CO2 eq. abated). The method is widely used in national and sector wide policy planning, but can also be used by companies and utilities to investigate which options are most cost-efficient.
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The data necessary to construct MAC curves are calculated according to the assumptions as sketched above. To calculate the specific costs per ton of CO2 eq. abated, the following formulas should be employed:
Where: Cspec, CO2 = Specific CO2 eq. mitigation costs α * ∆I = annualized capital costs ∆B = annual benefits (€) ∆C = annual costs (€) ∆MCO2 = annual amount of avoided CO2 eq. emissions (ton CO2 eq.)
The capital recovery factor alpha is determined by the following formula:
Where: α = capital recovery factor r = discount rate L = Lifetime
MAC curves are clear, easy to understand graphs displaying which (technological) measures reduce CO2 eq. emissions in the most cost-efficient way (Kesicki, 2011). It allows decision makers to see in one glance what the yearly costs would be to abate a set amount of CO2 eq. emissions (Kesicki, 2011). Additionally, the methodology makes it possible to cross compare different possibilities. Non-watercycle related projects can be valuated and compared in order to make a well-weighted decision with the greatest societal benefits. Finally, it becomes possible to create different MAC curves with different assumptions, hereby providing for sound sensitivity analysis of the results; for example in the case of energy price increase projections. MAC curve for water utility Waternet In the Waternet MAC curve under consideration in this paper, only a selection of measures was used. A societal perspective is taken to research the cost-effectiveness and the CO2 eq. abatement potential. It should be noted that this is by far not an exhaustive oversight of the possibilities in the watercycle to reduce CO2 eq. emissions. General assumptions The general assumptions use to construct the MAC curve for Waternet can be found below in table 1. General assumptions Discount rate r 6% Gasprize (excluding fixed right costs) 0.63 €/m³ Electricity price end users 0.22 €/kWh Table 1: general assumptions MAC curve
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Cold and heat regeneration of ATES systems Different sources in the watercycle such as surface water, waste water and drinking water offer the potential to gain or recover heat and cold. In the dense area of Amsterdam in which Waternet operates, an important source for sustainable heat and cold are aquifer thermal energy storage systems (ATES systems). Although well functioning, these system are often (deliberately dimensioned) out of balance, hence requiring extra heat or cold to increase its effective functioning. This heat or cold could perfectly be provided by the recovered sustainable heat and cold form the watercycle sources. Together with installation company IF technology an estimation has been made of the average extra heat and cold demand. Additionally, an estimation has been made of the number of current and future ATES systems in Amsterdam. We estimate that over 270 ATES systems will require extra sustainable heat and cold up to 2020. Low flow shower head A low flow shower head (LFSH) is a shower head which reduces the flow of water, theoretically speaking without reducing the level of comfort. CO2 eq. reductions by LFSHs principally come from the lesser water that has to be heated: a LFSH has a lower flow than a regular or a comfort douche. Currently, the penetration rate for LFSHs is 50% (Foekema & van Thiel, 2011). According to an estimated calculation of the potential renovation moments of bathing rooms in Amsterdam, approximately 4.500 LFSHs could be installed each year. Note that replacing a shower head is very easy, so the actual implementation is not necessarily limited by renovation moments. The average shower duration has relatively stabilized, and hence will not be regarded as a rebound effect1 on the warm water savings grace to the LFSH. The investment costs of a low flow shower head are assumed at €40. Drain waste heat recovery system A drain waste heat recovery system (DWHR system) is a heat recovering system that recovers heat from shower water. Shower waste water contains high quality heat. Furthermore, showering is often a daily activity and hence a constant use of the DWHR system is guaranteed throughout the year (Blom et al., 2010). On average, the shower water temperature is 40° Celsius, and the temperature after utilization 35° Celsius. Optimally, the recovered heat is utilized both to directly pre-heat the cold water for the shower as well as the water flowing to the boiler or the central heating system. As the heat is used directly for showering, no buffer or storage system needs to be installed. Current penetration rates are assumed to be negligible, and therefore the potential number of yearly renovations in which a DWHR could be applied is estimated at 9.000. The investment costs are estimated at €385. Cluster of measures at waste water facility The individual measures taken relate to the reduction of direct and indirect energy use and CO2 eq. emission through the increase of energy efficiency of processes, decrease of electricity use, the reduction of procured chemicals and resources, as well as through the increase of production of biogas at the waste water facility. The main component in this cluster is the production of 1
In this situation, the rebound effect would entail that the positive environmental effect is diminished or eliminated due to increase in comfort, such as longer showers.
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biogas, which accounts for over 90 percent of the CO2 eq. emission reductions each year. The total estimated costs of this cluster of measures is estimated at €8.000.000. Renewable energy: wind The reduction of CO2 eq. emission by means of installing capacity of renewable energy capacity has also been taken into account. A capacity of 30MW, provided by 10 turbines of 3MW as planned to be installed on Waternet’s facility ground. Based on the current investment and O&M prices of onshore wind energy, a reference production price was calculated of 0.074 €/kWh, as compared to the reference electricity cost price of 0.062 €/kWh. Results and conclusions Through researching the possibilities to undertake CO2 eq. emission reduction in the Amsterdam Watercycle, it became visible that there is a large potential, which could be easily translated to Waternet’s ambitions and policy targets for reducing carbon emissions in the watercycle. As indicated before, the potential for Waternet for reducing CO2 eq. might be substantially enlarged if for other options, for which the theoretical potential is already researched, more data would be present to investigate the deployment potential. The MAC curves methodology gives a clear direction of which data would be required to include more options as well.
Figure 1: MAC curve showing reduction deployment potential for Waternet in 2020, costlevel 2011.
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Figure 1 shows the cost effectiveness of each of the five measures in attaining CO2 eq. abatement. Negative abatement costs, as show the options under the x-axis should be considered as cost-effective opportunities to abate CO2 eq. emissions. As one can see, the most cost effective opportunities, which effectively save money, are the recovery options with the potential of heat and cold in the watercycle. On the other hand, the cluster of measures at wastewater facility appears to be costing a little, but has the largest CO2 eq. emission reduction potential. The production of renewable energy, at a 2011 cost level appears very costly, especially if one would compare these costs (close to 200€/ton CO2 eq.) to the ETS market price of carbon emission of around 20€/ton CO2 abated, which is estimated as the average market price up to 2020 (Geurts & Rathmann, 2010). For the decision makers at Waternet, it would now be clear what the potential CO2 eq. emission reduction is that could be achieved by these measures, how these related to the policy ambitions and target, and finally at what price these CO2 eq. ambitions and targets could be met. It should be noted that the governance issues of realizing the potential are not taken in to consideration. To realize the potential of the for example the opportunities in the household (low flow shower head and drain waste heat recovery system) close cooperation with individual house owners and housing corporations need to be sought. Equally, to realize the potential of heat and cold recovery, a connection has to be made to the numerous sustainable heat and cold demanding parties. Concluding we can argue that by providing this practical example of the use of MAC curves for water utility Waternet, the applicability of MAC curves for the water sector in their search for sound CO2 eq. emissions reductions strategies can be illustrated.
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References Blom, J.J., Telkamp, P., Sukkar, G.F.J., de Wit., G.J. (2010). Energie in de waterketen. Stowa, Amsterfoort. Foekema, H., van Thiel, L. (2011). Watergebruik thuis 2010. TNS NIPO, Amsterdam, as commissioned by VEWIN. Frijns, J., Mulder, M., Roorda, J (2008). Op weg naar een klimaatneutrale waterketen. STOWA, Utrecht. Geurts, F., Rathmann, M. (2010). Prijsbeleid voor een versnelde energietransitie. Ecofys, Utrecht. IF technology (2012). Personal communication Wijnand Vink. Kesicki, F. (2011). Marginal Abatement Cost Curves for Policy Making – Expert-Based vs. Model-derived Curves. Energy Institute, University College London, London. Mol, S., Kornman, J., Kerpershoek, A.J., Helm, van der, A.W.C. (2011). Opportunities for public water utilities in the market of energy from water. Water Science and Technology. 63,12. Van der Hoek, J.P. (2012). Climate change mitigation by recovery of energy from the water cycle: A new challenge for water management. Water Science and Technology. 65,1.
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