30/09/2016 Balancing Energy Efficient Systems and Renewable Energy Sources: Collaboration or Competition?

Transcription

1 Balancing Energy Efficient Systems and Renewable Energy Sources: Collaboration Gian Vincenzo Fracastoro DENERG Energy Department Politecnico di Torino 30/09/2016 Renewable Energy Sources: Collaboration 1

2 Nearly Zero Energy Building EU Directive 2010/31 According to the EPBD, a Nearly Zero Energy Building is a building that has a very high energy performance [ ]. The nearly zero amount of energy required should to a very significant extent be covered by energy from renewable sources, including renewable energy produced on-site or nearby. Still many people talk about ZEB - Zero Energy Buildings or 2 Competition?

3 Zero Energy Building You can minimize almost «as much as you want» energy demand for Heating Ventilation Air conditioning But in a lived house you cannot eliminate energy demand from Lighting and electrical appliances Cooking Domestic hot water 3

4 Still, we may reach a Net ZEB N-ZEB = a building having an energy demand equal to the energy it produces This concept has to be clarified 1. What type of energy? We must refer to primary energy. 2. What time-scale? Should Net Zero energy be zero at any time (need to store energy) or globally, on a year-base (need to be grid connected and use the grid as an almost infinite storage - at a cost)? 3. What geographical scale? Building scale or community scale, how large? 4

5 If we can count on a grid Part of primary energy produced in situ is directly used by the building Excess energy demand must be delivered to the building by the grid Excess energy produced is exported by the building through the grid 30/09/2016 Every energy carrier has to be multiplied by a primary energy factor f P,del. Then, for a NetZEB, the algebraic sum of energy demand E dem x f P,dem and produced energy E prod x f P,prod, calculated for each type of energy carrier (heat, gas, oil, electricity, H 2 etc.) must be equal to zero Renewable Energy Sources: Collaboration 5

6 We can reach a Net-ZEB or Net-ZEC (Community) Using a mix of Demand Side Management (DMS), Energy Efficiency (EE) and Renewable Energy Sources (RES) E p,dem E p,dem E 0 0 E 0 0 E E 1 E p,prod E p,prod Step 0-1: EE+DMS will reduce energy demand from 0 (normal building design) to 1 Step 1-2: RES will allow to reach the NZEB line Where is our target? 6

7 E (kwh) How to decide the mix of EE and RES? One possible criterion is to maximize the primary energy saved (and produced) per unit expenditure (kwh/ ) E 0 0 Start from most profitable actions/retrofits law of diminishing returns Step 0-1 = from normal to low energy demand building Step 1-2 = introduce RES E Grid-connected or storable energy straight line (e.g., PV) Off-grid law of diminishing returns (e.g., ST) C 2 C 1 C 2 Cost ( ) Use the slope indicator (kwh/ ) to rank measures to be adopted 7

8 Before we go further What is energy efficiency? We use energy, but what we need is not energy, we need services: A comfortable environment in terms of light, temperature, humidity, clean air at any time Hot water for personal hygiene A working PC, and electrical equipment at home and at work A way to produce goods from agriculture and industry A way to move from one place to another Energy efficiency doesn t mean reduce comfort (thermal, IAQ, light) Energy efficiency means Reduce the energy demand (Demand Side Management) Increase the energy conversion efficiency of appliances (EE) Use less energy, use it in a better way has no negative side effects! 8

9 Which RES are available at a building or community scale*? Depending on the geographical scale we may choose: Solar thermal Solar photovoltaic Ground-coupled heat pumps Wind? Biomass?? * The closer, the better! Is a kwh saved equal to a kwh produced by a Renewable Energy Source RES? Possible problems in urban contexts: Shadows Competition with ST Mutual interference Obstacles Pollution 9

10 On a wider scale RES: increasing efficiency, hi-tech industry, and decreasing cost, but production is elsewhere. DSM and EE: stable cost and performance, low-tech industry, local production In Italy: in , 22 billion invested in building retrofits with almost 5 Mtoe/year of primary energy savings (source: Enea). About 12 billion tax deduction In the same period, about 50 billion invested in PV (19 GW) with about 22 TWh (or, 4.3 Mtoe) produced every year, but with electricity bills increased by 6.7 billion /yr 30/09/2016 Renewable Energy Sources: Collaboration 10

11 Conflicting factors DMS, EE and RES are complementary when we want to reach a NZEB system, but also interrelated and sometimes conflicting among them. DMS measures make investments on energy generation (e.g., district heating) less affordable Higher efficiency of energy generation (heat pumps, condensing boilers, CHP driven district heating ) reduces the advantage of actions aiming at DMS (e.g., thermal insulation) 11

12 Example #1: Politecnico s heat Politecnico uses about 15 million kwh for heating Up to 2006 we used to produce heat through ordinary boilers, having an average efficiency above 85% 1 kwh th of heating demand reduction would make us save 1.18 kwh of primary energy Since then we have connected Polito headquarters (13 million kwh) to the Urban District Heating system. What is the primary energy savings we have achieved? What is primary energy savings for 1 kwh of demand reduction? 12

13 Example #2: Politecnico s heat heat Q distr losses primary energy E p CHP system Useful heat Q u Electricity W Which fraction E ph of the primary energy used should be attributed to heat production? Using the Ministerial Decree 15/6/2015 method, and the data from IREN concerning Torino s DH mainly fueled by CHP systems we find that saving 1 kwh of heat we only save 0.63 kwh of primary energy! 13

14 Example #2: Hospital We compare the PBT of polygeneration system based on a microturbine with heat recovery on exhaust gases with or w/o a single-stage absorption machine with the present conventional system (electricity from the utility, boiler for heat and steam compression refrigerating machine for cold). Present installation CHP system PBT in years Polygeneration system Specific cost ( /kw) Present building (no insulation) Wall insulation 17 > Wall insulation and High efficiency windows > 20 > 20 > 20 Result: the more efficient the building, the less affordable becomes the investment on polygeneration 14

15 Challenges/opportunities 1. How to combine energy efficiency with RES in a way that maximizes the benefits, both for the customer and society at large? 2. How to take into account mutual conflicts or synergies between RES and EE? 3. How to choose the best mix of RES for a building or a community and make them able to maximize the benefits of the chosen RES technologies? 4. How to teach all this? How to support correctly RES and EE taking into account the real economic and environmental advantages they may provide? 15

16 Open questions waiting for answers Thank you! 30/09/2016 Renewable Energy Sources: Collaboration 16